I don't think they are inevitable. I had one in the 1980s when I as racing, but my bike was too big, my saddle was not good (not too many choices back then), and my shorts had real leather chamois in them (not very soft at times).

I don't ride a trainer, so I can't comment on that, but what kermit says makes sense.

Have you checked your position and fit on your bike, and have you tried different saddles? Are your shorts too big and do they bunch up? Do they have seams in the chamois?