Did you miss the do it well part? Nearly every unix tool does more than one thing, the alternative would be a usability nightmare.

* grep, which primarily does pattern matching has dozens of file traversal related flags that could be handled by calling it from find

* find, a tool supposed to find files for some reason has dozens of flags related to executing applications which could probably be done by using xargs

* did you know that xargs can do pattern matching and replacement on its input string? there are probably dozens of unix tools that are specialized for that