For one, because we haven't done as much research on the long-term effects of semaglutide, especially on demographics it isn't current prescribed to. Fluoride, on the other hand, is well-researched.
I think there's a larger argument about invasiveness being something that we can also quantify, and intervening on obesity is more invasive than intervening on caries, as you've noted. But the research argument above is perfectly sufficient on its own.
If you don't like the smoking argument, consider enrichment/enforcement of foods (including public school foods). Iodized salt, enriched flour, fortified milk, etc.
I think there's a larger argument about invasiveness being something that we can also quantify, and intervening on obesity is more invasive than intervening on caries, as you've noted. But the research argument above is perfectly sufficient on its own.
If you don't like the smoking argument, consider enrichment/enforcement of foods (including public school foods). Iodized salt, enriched flour, fortified milk, etc.