Clichès fill up an imagined 'vacuum' in which many people seem to be uncomfortable, they can't think of anything to say, so they parrot a clichè to compensate for this imaginary deficit.
One of the justifications I received for clichès was that any stock phrase, even structured phrases, repeated widely and often enough, would eventually become clichès. I think this was mant to somehow legitimate the use of clichès, though somehow it never did quite justify their use to me.
It was never really this aspect that annoyed me so much as the fact that most clichès are supposed to contain a kind of 'condensed wisdom', which means that it expresses something that through force of rote repitition has gained an authority many orders of magnitude above that which it would ordinarily merit. The sentiment and opinion encapsulated by a clichè derives its authority through being widely perceived to be unchallengeable. It is this latter point that irritates and rankles with me, as well as the fact that people who use clichès are often co-opting this 'condensed wisdom' and passing it off as a property of themselves.
And now for some caveats:
Advertising slogans which carry a simple message can sometimes fall into popular usage. Similarly, some advertising campaigns can comandeer popular folk-sayings and clichès as a means of trying to sell the products of the advertising agency's clients.
I can't think of any examples off-hand, but there are bound to be some.
Something else that occurs to me is that some children can often hear of 'sayings', 'expressions' and clichès, then use them indiscriminately. At a young age it can be considered a novel use of language, even if one doesn't fully understand what they mean. I have to admit that I may have done this on more than one occasion myself, though the popular sayings in circulation tend to irritate me including (but by no means limited to), the perenniel "smile, it may never happen", '"turn that frown upside down", plus countless other vacuum-fillers people sometimes emit for the sake of making a social noise that is remarkably free of semantic content.