A Stock Rhyme is a kind of rhyme / that everyone sees all the time. The reasons for this can vary: the rhyme choice may be extremely limited, as with love, alternate rhymes may be unusual words that are not very widely applicable (fire/spire), or the rhyme may be particularly well-suited to a popular type of song like Silly Love Songs. Like with many stock tropes, a predictable rhyme can make an audience cringe, but a sufficiently awesome artist can often breathe new life into them.