I realise that humour is quite a subjective thing but all the same Catherine Tate is about as funny as infant mortality. People say sarcasm is the lowest form of wit but personally I think catchphrase comedy is several steps down from it. Most of her material has been crudely borrowed from other shows, some of which weren't really that good either.
Luckily for this stupid ginger harridan the good old BBC like to give out very long contracts as a result of having a few 'stars' poached by ITV about twenty bloody years ago. They never got over it and so the likes of Catherine 'talent vacuum' Tate are given five, ten or even fifteen year contracts. What this means for the viewer is whether they turn out to be any good or not they will be on your screen for a very long time.
I wouldn't really care to be honest but the BBC foisted her on Dr Who fans ruining that show as well. She has no talent, no charisma and she certainly isn't funny but you'll be seeing lots more of her I'm sure.