The tour says "Good answers are voted up and rise to the top." If you lump all of them together, how do the best of the answers rise to the top of the list? They might all be good, but now we can't vote on them separately so they can be ordered.
The compilation of answers into one answer makes things more complicated without actually adding any value. If new answers come along or the original answers are improved (or deleted) now the compilation is out of date. As separate answers, I can sort by "oldest", "active" or "votes" which let's me easily focus on the content I want to see first (especially important when you're on the mobile site).
I think it's fine to link to (or mention) someone's answer if you want to discuss it or expand upon it in your own answer, but just copying and pasting other people's ideas (even if they are attributed) into one answer isn't useful in my opinion.
The StackPrinter app is a better way to handle creating a compilation of a question and answer.
StackPrinter is a website that pulls the main details of a given question, all its answers, comments and votes formatting them in a simple essential printable view.
(it has a bunch of other nice features as well)