Lots of classes are balanced around their move speed cap, forcing them to make certain sacrifices to go faster than their walk speed, due to movement being so valuable. You can see this value in unlocks and mechanics that grant move speed: Heavy quickly has his health pool drained just to move slightly faster, Soldier is marked for death (or has to sacrifice HP and crit heals to blast jump), Demoman has to remove his powerful stickybomb launcher for a quick charge every so often (or again, blast jump and lose health and crit heals), Pyro gets damage vulnerability with her Powerjack, Scout loses his powerful ability to double jump with the Baby Face's Blaster (if he wants the extra move speed) and Medic has reduce his heals by putting away his medigun (and not equipping the crossbow) to use the Overdose (which also has a damage penalty).
Bunnyhopping doesn't have those risks. It adds a lot of extra move speed to classes who were balanced around some other move speed or movement mechanic. I don't think it has a place in TF2.