I think one problem is that both DH and RSA depend on the fact that finding inverses is hard in certain big groups, which isn't an intuitive idea.(Admittedly, i

I think one problem is that both DH and RSA depend on the fact that finding inverses is hard in certain big groups, which isn't an intuitive idea.(Admittedly, in RSA, the idea that factoring is hard is intuitive, but then you have the problem that the fact that the big composite number gives you a group, isn't). I always find it a shame that Fermat's Little Theorem, and multiplicative groups aren't taught earlier in a typical maths education, as the beauty returned from a small effort is significant.