Because the BBC is fucking shit? It’s government propaganda disguised as an independent impartial broadcaster.

Yes it makes some good content with some good talent that may make you laugh but institutionally it’s anti Scottish, pro Palestinian genocide, downplays climate change to almost denial, and uses false balance to push the Overton window rightward.

en.wikipedia.org/wiki/BBC#History

en.wikipedia.org/wiki/BBC#Controversies

en.wikipedia.org/wiki/Criticism_of_the_BBC

en.wikipedia.org/wiki/BBC_controversies

en.wikipedia.org/wiki/BBC_independence

You need read any one of those Wikipedia articles to find a list of reasons for disliking the BBC. I recommend starting at the beginning though and going with History first of all.