Languages that are easier to throw together a reasonable parser for (Lisps, Smalltalk, Lua, or even C) have a much lower barrier to entry for development tools. Keeping the language syntax simple enough means that somebody scratching an itch can write something useful in an afternoon or a weekend, rather than taking a team and months.
For an example of a less accidentally complex way to do what C++ templates do, look at ML's functors.
Heck, even Java.
People (rightfully) complain a lot about how verbose some parts of java are (like how instead of anonymous functions or functions that can be passed as a parameter you have anonymous classes), but ignore the fact that the designers intentionally made that sacrifice to maintain consistency.
I'm working on a tool to help maintenance coders undo the damage from copy-and-paste programming on huge legacy code bases. One approach it uses is language-specific, but requires a bit of configuration (via Lua's wonderful LPEG), and the other is language agnostic. It's searingly obvious how much worse C++ is in this regard.