It's not so much a case of people not listening, it's just that Scald isn't that great on Keldeo. It's a fast and powerful offensive Pokemon, and it honestly should be utilized as such. Scald is mostly a support option, and it suffers from a low base power. The burn rate is nice and all, but you have to ask if it's worth losing a significant amount of power in comparison to Hydro Pump. If you need a more reliable STAB option, you might as well go with Surf. It still has solid power and solves the accuracy and PP problems that Hydro Pump has. Not that Scald is a bad move for Keldeo, but it's definitely Other Options material.