I sometimes refer to this practice as "writing on auto-pilot." Most people, if they habitually allow themselves to write down the first expression that occurs to them in describing something, end up populating their writing with a surprisingly large number of clichés. This happens quite naturally because clichés tend to rise to the top of the expression grab-bag in any particular situation.
One problem with cliché-riddled writing is that (as you say) the writer may not have looked very deeply into the cliché to see whether it really captures the idea that he or she is trying to express. Another problem is that, even if the cliché does capture the idea appropriately, readers may receive it with insufficient consideration because it is so familiar to them as a prefab expression. A string of clichés may be perfectly apt—perhaps even profoundly so, in the right context—and yet leave many readers glassy eyed and unmoved, simply because the expressions have, through overuse, lost their original sharpness and ability to incite insight.
It takes effort (or an unusual mind) to avoid automatonically resorting to set phrases for the multitude of things that a writer (or speaker) wants to express. In the bog of everyday speech, clichés may provide familiar, secure footing for listeners who are trying to keep up with the speaker. But readers expect writers to offer a more carefully conceived expository path, and preferably one that doesn't mindlessly recycle clichés at every tenth step.