To answer your question directly: If you're grepping through source code, you generally do not care about caches, backups, personal workspace configs, node_modules, "compiled" output (JS projects generally "compile" to JS and if you're looking for something in source files, you probably do not care about the bundles you're outputting, just the source), etc. You generally care about your source code, which is the stuff that's not getting added to .gitignore.

Since we're talking about an open source project, try to keep some empathy for developers that are solving their own problems first and not trying to solve everybody's problems. It's a configurable option, anyway.