Well it appears they happen for US crews too. I'd just be happy if I could get my whole crew trained in one normal skill like I could in SH3.
Something else I noticed...the US subs all seem kinda inferior to the German subs. Germans have better guns, better torps, and more advanced subs. US subs almost feel like they are from WW1. I mean even the "normal" German subs like the Type IX are far better than the best US versions. I guess it was that way in WW2 too. Just we had more boats than them. Quantity over quality. Not saying US subs are garbage or anything. Just not as good as the German ones.