I always thought it is a way for some people to not get themselve into trouble.

Similiar to the blinds: over the long run many players lose money in the blinds, not only because you have to put in money in with marginal hands, but because you might make more mistakes because you get into difficult situations easier. How often have you completed as the SB, just to flop middle pair?

Could be the same with folding when you could check. Maybe they have something that they know will get them in trouble, so they just fold it right now.