What is it about landing on grass?

[FNG]

I've noticed in a few threads recently that quite a few people have never landed on grass and/or aren't allowed to by their groups/clubs. Leaving aside people who fly mega twins, turboprops or whatever, (although as far as I know some of these land happily enough on grass when depositing jockeys at Newmarket and other such places), and assuming that people are flying the usual range of SEP aircraft, what is it that keeps people off the grass?*

This really is not intended to be a "grass roots flyers vs spam can drivers" thread (after all, plenty of people learn in spam cans at grass airfields), but is a genuine enquiry as to what people are told about grass runways by schools, clubs etc. Are there any statistics to suggest that operating on grass runways (leaving aside short farm strips) leads to more accidents? I cannot see why there should be.


* I refer, principally, to grass runways at mainstream airfields rather than small grass strips.