Curving the top tube on that newer Marin serves no function at all. The curve in the down tube is dubious at best. Old bikes never had it, and I don't think needed it either. In all my years as a mechanic, I never saw damage on the down tube from the fork crown hitting it.
Damage on the top tube from the handlebar, sure - saw that all the time. The bars probably hit way before the crank.
Maybe with today's short stems and stupidly wide bars that doesn't happen any more?