Players, as a whole, tend to be maximizing-oriented when they create a character.

Everyone has different priorities, but the majority of players all try to maximize one or two things, sometimes more if not mutually exclusive.

Very few people roll a warrior and then say, "Ok I want to be protected accross with saves, have 30 dam roll, 1100 hp..."

Most would say, "Alright, I can get a full set of pwent, and if I stack Chilling Embrace on that I can get 90 dam."

The same goes for Soul of the Mountain. *Most* of the time a player will think, "Wow, my dwarf has 1500 hp! If I take Soul of the Mountain, I'll have 1700!!!!"

Not very many think, "Hmm, my hp are slightly below average, let me spend a legacy on achieving mediocracy."

It's just not how people work. While these legacies are perfectly fine for low str, low con races, it's simply not who's going to use them most frequently.