Petty ran into the same brick wall that stymied Fairuza Balk's career: execs didn't see her as a romantic lead in mainstream films. In the 90s, success in a romantic mainstream film was the surest path to building a solid career. Being that roles for women were (and are) so few, the only other viable path was being in a surprise success that created an image (e.g., Kathy Bates in Misery or Juliette Lewis in Cape Fear). I'm sure Tank Girl was meant to be that for Petty, but it wasn't the success she needed at the time.

Mathis, on the other hand, was getting cast as the romantic lead in the early 90s, but none of them were hits. Had Pump up the Volume or That Thing Called Love done well, she probably wouldn't have been in a very minor role later in the decade in The American President. She's also talked about how River Phoenix's death really messed her up, as you would imagine.

Both should've been in way more stuff. But then so should have Fairuza Balk, Robin Tunney, Martha Plimpton, Lili Taylor, etc. The 90s did a shitty job of utilizing the talent available.