I don't think they deemed it "useful":

  We’ve never supported ASCII tab; ChatGPT was outright lying to people. And making us look bad in the process, setting false expectations about our service.... We ended up deciding: what the heck, we might as well meet the market demand.

  [...] 

  My feelings on this are conflicted. I’m happy to add a tool that helps people. But I feel like our hand was forced in a weird way. Should we really be developing features in response to misinformation?

The feature seems pretty useless for practicing guitar since ASCII tablature usually doesn't include the rhythm: it is a bit shady to present the music as faithfully representing the tab, especially since only beginner guitarists would ask ChatGPT for help - they might not realize the rhythm is wrong. If ChatGPT didn't "force their hand" I doubt they would have included a misleading and useless feature.