Metformin is well-understood, old, safe, and has various health benefits.

Surprisingly, metformin seems to be almost a pure win, even for healthy people: https://www.health.harvard.edu/blog/is-metformin-a-wonder-dr...

In contrast, GIP analogues like semaglutaide present real risks and are less well understood. For some people, with serious health problems, GIP analogues make sense. But generally you don't want to be taking them if you're healthy.