I can remember watching Spitting Image when it was new and the novelty of seeing notable 'serious' people being lampooned as foolish, vain, stupid, idiotic, ignorant, with all the usual human vices, was quite exciting. After a while though, one came to realise from media reports that the lampooned figures were, for the most part, exactly like that. After one realised this, the programme stopped being funny and just came to be a slightly-exaggerated view of what was actually going on in Britain.  

 ::::Making fun of pretentious people is good entertainment, but once one saw what many of the lampooned politicians and personalities would actually do in real life if asked-to or paid to do, then the programme stopped being funny. A bit like kicking a cripple's crutches away, really. Not really funny portraying a prominent politician as being a corrupt, lying bastard, if a court subsequently convicts him of being all these and more. 

 ::::The programme only worked when the people being lampooned had any public credibility. This credibility had almost disappeared from public figures by the time of the programme's demise.