Over the course of the 2017 regular season, Pittsburgh Steelers quarterback Ben Roethlisberger played a total of 1060 snaps, factoring in everything, including no-plays, pre-snap penalties, two-point conversion attempts, etc. he only lined up under center for 295 of those plays, or 27.8 percent of the time.
This data is taken from our own charting, which we spend hours upon hours of doing every single season. While he is probably an example of the extreme end, however, he is a representative of the fact that NFL offenses are slowly moving away from prioritization of playing under center, for all the ails and ills that provides.