It's not that he isn't capable of doing so—Williams started 38 games for the 76ers in the 2009-10 season and averaged a respectable 14.0 points per game on 47 percent shooting that season.
Lack of opportunity isn't a valid explanation, either. Until Evan Turner replaced Jodie Meeks in the starting lineup on March 5, the team could have easily slid Williams in the backcourt next to Jrue Holiday.
So why is it that the player who leads the team in scoring (15.8 PPG) hasn't started a game in nearly two full years?
The answer is simple: Williams is far more valuable to the 76ers coming off the bench than he would be as a starter.
Philadelphia's second unit is among the best in the league, and the primary reason for its success is Williams' ability to provide an instant scoring punch as the team's sixth man. The 6'1", 175-pound Williams compares favorably Vinnie Johnson, an undersized "scoring guard" who shined in a reserve role for the Detroit teams of the '80s and early '90s.
Affectionately referred to as "The Microwave" for his ability to quickly "heat up," Johnson played behind two future Hall of Famers (Isiah Thomas and Joe Dumars) and still found a way to average 12 points or more for seven consecutive seasons with the Pistons.
Not only does Williams—who has averaged double-figures in each of the last five seasons—have a similar skill set, but he also has an incredible knack for knocking down shots that are practically indefensible.
"He's very good at shooting deep threes," Collins told SI.com earlier this season. "A guy will think Lou is out of his range, and suddenly he'll pull from 30 feet."
No one on the 76ers—and perhaps few guards in the league—can draw contact from defenders as well as Williams. No one on the team can create his own shot better than Williams, who has picked up quite a few tricks of the trade during his six-plus seasons. And his phenomenal assist-to-turnover ratio of 3.06-to-1 is good for sixth in the NBA.
All of which are reasons why Williams is just fine where he is. As the first man off the bench each game, he can either extend his team's solid start or give the 76ers a much-needed boost if they happen to come out of the gate a bit sluggish.
"When [Williams] comes in the game, we know what to expect," center Spencer Hawes said earlier this year. "When he starts rolling, he kind of takes everyone with him."
Philadelphia's reserve unit is noticeably weaker now that Turner has ascended to the starting two-guard spot, and a theoretical swap of Holiday-for-Williams in the lineup—as some have argued for—would only serve to disrupt the chemistry of the 76ers' "Night Shift."
In basketball, it's not about who starts the game, but rather, who finishes it. And for the 76ers, Lou Williams is usually the one with the ball in his hands at crunch time.
If you were to ask Williams, he'd likely tell you that being the team's de facto "closer" is far more important than having the designation of being a "starter."