Little kids think that 'being silly' is the same as 'being funny'. As we grow older we tend to be more selective about what we find funny. However some 'plain silliness' continues to amuse many people.
For example, the Goons and the Monty Python team both relied heavily upon the assumption that people would equate silliness with funniness. At their best ("What time is it, Eccles?" and the Dead Parrot sketch, for example) they were brilliant but only because of the structure which was built into those sketches.
Unfortunately there are 'comedians' (e.g. Reeves & Mortimer) who, like five-year-olds, continue to think that unstructured silliness is funny. The fact that they win awards indicates that some of their audience must agree.
Miranda Hart?
Well, she's a passable stand-up comedian but she's got no acting ability whatsoever. Whoever it is who puts people like her and Lee Mack into sitcoms (where the roles could be filled a zillion times better by a properly trained actor) should lose their job!