*shrug* I haven't experienced that. I've only seen the computer go for it in situations that make sense. Maybe one 4th down attempt every other game, maybe 2 out of 3 games. I'm in my third season of Dynasty, so I think I've got a big enough sample size.
I see the computer go for it when they're in borderline field goal range. I don't think I've ever seen them go for it in their own territory.