Shukuchi is not something that you use whenever you need to move, it has it's niche uses. For example, several fights in the game has ice floor mechanic, where if you move normally, you will slide around uncontrollably. Shukuchi allows you to still move during this mechanic. But it's real use imo is for min-maxing dps at the end game raid. If the use is pre-planned (and with a bit of practice), it is not hard to execute anymore and can get in a couple more hits before you are forced to disengage from the boss.

Similarly for sprint, which incidentally certainly has a stamina system in the form of tp. In a fight, using sprint during certain mechanics can really help you deal with them more easily. But it has limited usage (even for casters who don't otherwise use the tp), so you are forced to plan when you want to use it. For melee, using it obviously requires even more consideration (will using up all these tp hinder your ability to deal damage later on, and if it does, by how much and is it still worth it).

Out of combat though (and especially in towns where you cannot use mount), I do feel they should just let us sprint infinitely.