It's important to draw a line between the way things should be and the way things are. Your mom is right, OP. If you're interviewing for white-collar jobs, openly displayed tattoos are probably a no-no. It ultimately depends on how conservative (small c) the company's corporate culture is, but as a general rule? It's better to cover them if you really want the job.
Context matters a lot for things like this though. Are your tattoos obvious? Is it just a tiny little kanji on your wrist or something like that? Are they offensive, or could the imagery potentially make others feel threatened or intimidated (a knife, for example, or snakes coiling around your neck and displaying their fangs)?
There's no one size fits all approach - but these things are seen as warning signs by HR departments, subconsciously or otherwise. Also, keep in mind - this is just one factor, and it comes in degrees. Someone coming out of an M7 MBA program with a 4.0 GPA and a couple of prestigious internships should be able to overcome the social stigma of a tattoo. That kind of a person represents too much of a potential asset to employers for a tattoo to ruin their chances entirely. But if you're pushing 35 with a relatively empty CV and limited education? In that case, your tattoos probably won't be doing you any favors in the "stereotype" department. That sucks, but it's something to keep in mind.