It's desirable if you're really focused on performance – if you're not a site like Google/Facebook which people access all the time, it's safe to assume that none of your resources are cached and so you might find n milliseconds of load time a healthy gain (less so now that HTTP/2 is widespread). In many cases it's more likely that you'd know of a bug fixed in a new release – where you'd say libfoo >= 1.12.4 – than that 1.3 has a huge problem.