There's two sides to this:

1.) You can jump in WoW, and many people here have inexplicable hatred for WoW, and they are afraid that anything in WoW that shows up in FFXIV will be turning FFXIV into a "WoW Clone".

2.) In WoW, other than a few specific places, the jump feature has no purpose other than to allow its players to hop around like ninnies.

I'm of the mind that it would be nice to have a jump feature similar to--and it pains me to say this--FFX-2, where scalable walls and small gaps are context sensitive, and the option to jump is given only where it is needed.

If SE re-examines their maps and how they handle ground and barrier collision, a jump feature may not be necessary, but that would be a lot of work to do for something that can be easily solved by simply letting us jump over small obstacles.