Because you don't need to hold the cue at the very bottom .
58" is actually long for most people.
Most hold it within the wrap section .
Johnny Archer plays with a 58".
So, does Jose Parica."
If you are 6'4", then maybe a 60" would be better for you .
But, there is no reason why a 6'0" person can't play with a 58".
Unless he has a really long bridge .
Cues are not like golf clubs .
You have to hold the club near the end and they can be too long or too short depending on your stance .
I've never had a request for a cue longer than 59" .