That only works if the ISPs are in direct competition, which for the vast majority of the country, are not.

Most US markets are effectively duopolies or "triopolies" at most. But even then, that's really stretching it. Because while two or three ISPs cover a city or metro, the neighborhood one lives in really determines the carrier. This part of town might only get cable from Comcast. While another part of town only gets it from Cox. That's really simplifying it, as maybe a consumer also has (slower) bonded DSL in their area, plus there's also home 5G and now Starlink. Fiber (either FTTC or FTTH) has made good headway, but it's still not ubiquitous. Your house or apartment building might have fiber; the one next door doesn't.

So there's a teensy bit of competition. But not really.

Cellular service has seen some of that competition on being honest with fees, but that's because of MVNOs. But traditional non-wireless ISPs really don't have that competition.