At least at the football games I've been to, the videoboards aren't primarily used for ads but to show score information, close-up camera shots, instant replays, gimmicks to hype up the crowd, etc. There's some advertising but it's usually in the form of the announcer saying "now let's watch the best plays of the year, brought to you by some random insurance company!" Most of the ads are old-fashioned paper billboards placed next to the videoboards, and not in distracting places like on the sidelines.

Televised football is totally different -- the ads are absolutely obnoxious. But I guess if you actually buy a ticket then they're incentivized to actually give you a good experience. Maybe NFL stadiums are worse than college stadiums, or maybe my school is just unusually pleasant, I don't know.