Is switching between semaglutide and tirzepatide something people actually do, and why?

It does happen, most commonly when someone plateaus on one medication, experiences side effects that don't improve, or simply wants to try the other given tirzepatide's somewhat higher average weight loss in trials. It's a decision made with a provider rather than something people typically do on their own, since switching involves its own dosing considerations. References: https://obesitycanada.ca/healthcare-professionals/adult-clinical-practice-guideline/

Switched after plateauing on semaglutide for a few months, saw more movement again after switching, though obviously that's just my experience not a guarantee for everyone.