Funny you should ask this question on HN. Have you read PG's essays on Lisp and the competitive advantage it granted his team in developing ViaWeb?
Your question might be about PLs, but in effect you are asking why somebody would prefer one abstraction over another.
Personally, I find it difficult to read and grok math. But if I write out stuff in Lisp s-exprs and use meaningful names for functions, etc, then I generally can understand a little bit better. Being able to "execute" such descriptions helps further.
Languages such as Lisp, Scheme, Smalltalk, Self (of the ones I'm familiar with) have simple syntax and powerful abstractions. They failed to gain "market share" due to perceived failings. However, they adhered to the philosophy of Occam's Razor.
I'll probably get flamed for saying this ... when you look at systems written in Lisp, the debates tend to boil down to people arguing over whether their abstraction is better than the other guy's. With a powerful language you can do anything in any way you choose. So the abstraction becomes the differentiating factor. Hence the emergence of not invented by me syndrome.