The simple answer is that it isn't a bad thing. Network drives are perfectly safe to map as drives.
The superstition comes from the fact that you shouldn't be mapping foreign (i.e. Internet) drives as local because files opened from mapped drives are opened using the "local" zone, which generally affords them less protection - and if the files are actually coming from the Internet this is a reduction in security.
If, as I suspect is the case, you're actually mapping intintranetnet network drives, then opening the folders as mapped drives is exactly as secure as accessing them via their network path names. The only difference is that having them mapped is more convenient.