"Training in them is good for agility and timing"
Voted for that one.
To ob2c, no, I can't think of any other way to improve agility and timing. The jumping kicks also develop power. Look at how other athletes in different sports. They consist of ballet, plyometrics, power and Olympic lifting, tai chi (just the exercises), and guess what... A lot of hip movement.
Chances of using a super jumping high kick in a real fight is slim. Very slim. I have used it a couple of times and it worked, but the only reason I even did that was I saw a huge opening and the both of us were very tired anyway. But again, in a fight, simplicity. Simplicity is the height of cultivation. But my motto goes, if you can kick high fast, you can kick low faster.
Using a jumping or fancy maneuver in fighting is like someone with the ball jumping in the air in football. You jump in the air, you have no force behind you. Then crack, you're on your back, wondering what happened. A lot of fumbles happen when the guy is in the air and gets drilled. The time comes where you do have to jump or hop, especially over those pesky defensive backs but all in all, it's rare. However, with fighting, the chances of using a jumping kick is even less than someone with the ball jumping in the air. Maybe as a touchdown dance you can jump around all you want, but jumping around after a victory in a street fight... Not a very smart or moral thing to do.
The only reason I even teach the people at the club high kicks is mainly for those reasons, for indirect training. It not only helps in combat, but in regular athletics as well. Correct plyometric training could shave .2 off your 40 yd. dash, make you be able to cut better, jump higher and explode in the air faster. Makes you explode off the blocks, it helps your balance, it helps your coordination.