I've written some toy compilers, and I can at least say:

  1. compilers have bugs
  2. it really sucks not knowing if a bug is in your code or in your compiler
  3. it sucks not having a source-level debugger

Anyone can write a simple compiler, just like anyone can make a simple database. The hard part (at least for a non-optimizing compiler) isn't the comp-sci theory, it's making the tooling around, and the extensive amount of testing needed to be sure you don't have subtle data corrupting bugs lying around to bite you.

I won't categorically reject the idea, for instance I think Facebook writing their HipHop compiler was completely defensible. But you need people with compiler experience, and people who know the pain of working with crappy, undocumented, buggy toolchains to make that decision, not people who once took a compiler course.