YouTube actually does block sponsor spots in videos if you have Premium. They call it "Skip Ahead" and don't really talk about sponsor spots, but practically speaking it's 9/10 just the "skip sponsor segment" button.
I remember about 10-15 years ago YouTube actually did try to ban sponsor spots in videos, but the backlash from creators was strong enough that they walked that back to "ok well we'll allow sponsor spots but you can't just insert the sponsor's own ad, it's gotta be your ad read and B-roll".
I remember about 10-15 years ago YouTube actually did try to ban sponsor spots in videos, but the backlash from creators was strong enough that they walked that back to "ok well we'll allow sponsor spots but you can't just insert the sponsor's own ad, it's gotta be your ad read and B-roll".