As someone that pays for YouTube premium (and isn’t served ads), I don’t understand why they push Shorts to me too. Presumably they should want me to spend the bare minimum amount of time on YouTube necessary to keep me subscribed, as any further use just contributes to higher infrastructure and bandwidth costs.
they don't want you to realise that you're not watching it much and cancel your subscription
Infrastructure and bandwidth cost savings aren't worth the risk that you start spending time on Netflix and cancel your subscription.