Anyone work with bellows on DSLRs

I first acquired a M42 simple Pentax bellows and, now, a genuine Pentax Auto Bellows I for my K100DS. It amazes me that you cannot directly fit a bellows to this camera and, presumably, the more recent DSLR models. I will have to get extension rings and use at least the shorter one so the bellows can clear not just that front overhang but even the basic mount frame. I take it that with macro lenses, bellows aren't used much anymore.