Fates are still a source of Spiritbond for low level materia. Due to Extract Materia, the prices of these are still significantly cheaper than in the past anyway. I see no reason to revert something that would cause stress to the server over a few worthless materia.

What they could do however, is add a Materia section to the poetics vendor and allow you to buy all outdated combat materia (grade 1-6).