grep with regexp misses any and all context. Especially in large codebases (and if terms are somewhat generic like "account", which can find hundreds of functions).

So, on small codebases it misses "small" things like "I've tried to re-implement the same frigging component 15 times already" or "just because it says account doesn't mean it is any way shape or form related to account billing".

On larger codebases it becomes worse and worse, since there's more functionality, more code, and agent's context window gets polluted very quickly.