A lot of people like the fact that h and l stop at line boundaries. It
lets them press it repeatedly or with a count without worrying about
wrapping to the next line. Additionally, there is a possibility that
plugins and mappings assume this behavior and will break if you have
them included in whichwrap.
But it's really all a matter of preference. Personally, I like having
them wrap. I've never found a situation where I wish I hadn't set them
up to do so.