Because it's really useful if you use it right. Normally you're creeping from cover to cover, but you might be able to sprint to a new cover, or that one nearby terminal, even if it looks a little risky. If it used quite a bit less energy, I personally could really abuse it and get away with a lot. I'd probably get a little bored with how easy it's exploited.

Sure it's possible, but that's no reason to nerf it to a laughable amount of use, nor to require an upgrade to do what a fit person in real life can do for 50 metres without problems.
All good game mechanics can be exploited in some way.

As it stands now, I cannot run my guys away from any soldiers, because it literally just has enough to take them across the street.
If they wanted to make it more fair, they should've just made sprint able to take you about 30 metres and had lighter units like dogs and light infantry be able to sprint as well.
There have been a good handful of times when this maneuver would've saved my squad instead of requiring a full respawn. :-s

They are running most of the time. The energy draining sprint is some unusual kind of boost, considering you can also "fast-creep" with it. That happens. If you could simply run away from danger easily, all the time, where would the challenge be? Might as well have a "teleport to safety" key.

Don't run around in the open. Go into alleyways, or places with lots of angles around walls, to try to break their line of sight. Then hide behind cover until they call off the chase.

And, if you get caught by someone who you don't have a bad reputation with, they will generally just escort you offsite. Just don't have your weapons drawn, and let them apprehend you.

I've never actually let my guys get captured. :-)
When they get noticed, THAT'S when I need the 50 metre sprint, to run away.

The sprint is meant to be used so you keep from getting discovered. If you only use it to get away, it will not work for you.

Sure, regular people might run 50 meters easy, but with a metal skeleton, a gun and a bigger firearm? Probably even grenades, drones and more.

They really do have to nerf it, because its a tactical game, about either moving tactically around taking cover and killing the enemies, or stealth / sneak past the enemies.

As it is now it already feels too powerful.