How do you ask a textbook a question? Exercises are great until the student is stuck at some "core concept" they could simply ask or explain their confusion and get a direct answer.

GPT very naturally encourages you to write out questions. That by itself can be useful for learning. You can even get answers for your questions.

And for a well trodden basic technique like mathematical induction, GPT is probably 'smart' enough to be able to explain everything.

Basically, most questions a beginner might have are already covered in something like Stack Overflow, so GPT 'just' has to give you the right cached answer, instead of coming up with new thoughts of its own. (This is very hand-wave-y.)

Isn't it obvious? I can't have a conversation with an exercise and the solution. ChatGPT has helped me uncover gaps in my mathematical knowledge because I can ask it questions about what something means, how something was arrived at, or how it works. Sometimes proofs involve logical "jumps" that aren't immediately or intuitively obvious, or require some mathematical maturity that I otherwise wouldn't be aware of. Something I would've otherwise needed a tutor for to determine.