Indeed sometimes using a module is overkill. However in a lot more cases, _not_ using a module is dangerous. I'll take overkill over bugs any time.
Some tasks look deceiptively simple. Parsing CGI parameters, CSV data, or XML (of course!) for example are all tasks that might look simple, but really aren't, and you are much better of using a well tested module than rolling your own code. Using modules also cuts down on development (and question-answering!) time, so why shouldn't we advocate it?
Finally, if installing a module is a problem for a newcomer, in the long (and even short) term, then helping them overcome that fear is doing them an even better service than solving their immediate problem.
That said, feel free to spend the time answering questions qith just core modules if you feel like it ;--)