The reason is simple: He's exactly the same quarterback today as the one who came out of Florida State when Tampa Bay selected him with the No. 1 pick in the 2015 draft.
Winston left the Seminoles program as an elite prospect with character red flags, the most serious of which was a rape allegation. While he served a three-game suspension for alleged sexual assault to start this season, his on-field performance has created cause for concern as well.
The 2013 Heisman Trophy winner struggled with turnovers in college, especially due to an inability to see the entire defense. Nothing has changed over the subsequent three-plus seasons.
"Decision making not consistent with his football intelligence. Will throw into impossible windows rather than taking safe throw underneath. Elongated windup and release allows instinctive defenders to close on throws. Was too easily baited into dangerous throws. Struggled with intermediate passing game in 2014, completing 56.8 percent of his passes with FBS-leading 11 interceptions in that range. Still learning nuances of position and how to move and hold defenders with his eyes. Would sleepwalk through first half of many games. Inconsistent footwork and weight transfer caused balls to sail. Prone to emotional outbursts on field. Quality of decision-making drops off substantially when pocket becomes turbulent and he's forced to leave it. Lacks athleticism to extend plays for very long outside of the pocket. Off-the-field character and ability to lead on NFL level are his primary obstacles, according to NFL evaluators."
All of this—every single part—was on display during Sunday's 37-34 loss to the Cincinnati Bengals before Winston was benched for Ryan Fitzpatrick.
"I'm definitely the reason why we came up short," Winston said, per The Athletic's Greg Auman. "... I own that. I have to fix it. There's not much that I can really say, but I can't turn the ball over."
One play nearly encapsulated all of it:
Decision-making not consistent with his football intelligence? Check.
Will throw into impossible windows rather than taking safe throw underneath? Check.
Was too easily baited into dangerous throws? Check.
Would sleepwalk through the first half of many games? Check.
Quality of decision-making drops off substantially when pocket becomes turbulent and he's forced to leave it? Check.
Lacks athleticism to extend plays for very long outside of the pocket? Check.
One isolated play doesn't capture any individual performance in its totality. However, Winston threw three more interceptions before being yanked—which only built upon a long-term track record, as ESPN's Trey Wingo noted:
Winston is a turnover machine, plain and simple. He's tied for the league lead with 10 interceptions despite having played in only four games. According to NFL Research, he's in one of the worst turnover stretches in the last 30 years:
NFL Research @NFLResearch
With 4 INT today, Jameis Winston has thrown 2+ INT in 5 straight games extending back to 2017 (T-Most since 1990) His 13 total INT in that span are tied for the most in a 5-game stretch over the last 5 seasons — with Ryan Fitzpatrick, the man who just replaced him in the game
Obviously, the Buccaneers chose to ignore these inadequacies. The franchise can't any longer, because the potential long-term investment at quarterback is far too significant.
Finding out Winston isn't the answer now is far better than it happening later in the process.
In April, Tampa Bay chose to pick up the quarterback's fifth-year option on his rookie contract at $20.9 million. General manager Jason Licht called the move a "no-brainer" at the time, per The Athletic's Greg Auman.
The no-brainer decision has turned into a Homer Simpson-like "D'oh" moment.
Impending financial implications should have those in charge doing an about-face regarding all of their previous decisions.
Winston's fifth year becomes fully guaranteed if he's injured at any point this season. However, the team can release him without any cap implications this offseason if not. Right now, the best possible option is to demote Winston to third string and play out the final nine games with Ryan Fitzpatrick behind center.
It's not a bad plan considering how the 35-year-old signal-caller has played during stretches.
He came onto the field Sunday and led an 18-point comeback before the Bengals captured a victory courtesy of a last-second 44-yard Randy Bullock field goal. Fitzpatrick, who started the first three games, completed 11 of 15 passes for 194 yards and a pair of scores in just over a quarter of play.
His effectiveness is only half of the story, though. Watch how Fitzpatrick's teammates react after the game-tying two-point conversion:
Winston's ability to lead can still be questioned (check), while it's 100 percent clear the team responds differently with Fitzpatrick in the lineup.
Still, head coach Dirk Koetter wouldn't commit to either signal-caller after the contest.
"We don't need to talk about it [today]," Koetter said, per Auman. "I mean, today is not the day I have to decide that, right? We don't have to talk about that today.
"I don't have any problems making decisions, and I will make it when the time is right. Now is probably not the right time to make it."
The decision seems rather simple.
A veteran bridge is already in place. The organization can make re-signing the 14-year pro a priority this offseason, release Winston at no cost and draft a different long-term option during April's draft.
Right now, the Buccaneers are caught in NFL limbo, which occurs when an organization over-invests in mediocre talent at the game's most important position.
Winston isn't the answer. He never has been and never will be.
Brent Sobleski covers the NFL for Bleacher Report. Follow him on Twitter: @brentsobleski.