Yeah, it's sad to see champions giving up chess in their 30s but I can also see the desire to leave on a high note, before you've declined, and also spend your life on other things- you've already shown you're the best so why invest all that time and effort into keeping your title? There's definitely diminishing returns.
If you're talking about competitive players, they don't give up, they stop competing professionally and usually go on to teach. Competitive chess is a gruelling full time job.
