I won't pretend to be an expert on this, but a lot of people spend a lot of time trying to figure out how to beat the doom tower stages with the lowest amount of turns possible.  

I believe it's possible in some situations to even get 0 turns, assuming your champion is slow enough and you rely on counter attacks.  I think some of the old Baron strategies revolved around this.  It is also free to keep trying the stage over and over until luck gets on your side, so for a dedicated player, it is all but inevitable once you have a solid build.

In all honesty it is actually quite fascinating why players do this, considering there isn't even any real rewards to do so, but each and their own

As Rose pointed out, the minimum number of turns per stage is actually 0. This is done in two main ways, that I know of: Retaliation gear, and relying on good RNG with a slow champion with AoE on their A1 (like Skullcrown and Sinesha).

The other is letting your champion(s) being constantly hard CC-ed as much as possible, which is what I do on Scarab. When they are provoked, for example, they are technically not taking a turn since they have no choice in what they do (they are literally being controlled). Therefore, the game doesn't count those "turns"as turns.

One other example is Nether Spider. The lowest turn count is done with Geomancer being the fastest and putting his HP burn on the mother spider. He is followed by someone to put Heal Reduction on the main spider. The other champions are A1 AoE champions that then attack everyone, spiderlings counterattack - but the game treats spiderlings as part of the main spider - so Geo's passive deals massive damage to the main spider every time the spiderlings counterattack.

As to why we do it - bragging rights, of course! What else?😉

You guys knocked those answers out of the park.

The minimum turns race strat I "enjoy" the most is Refresh Roulette with those poison explosion comps, where refresh accessories and many many retries are used to get through waves without even needing a reset champ like Kymar.

And by enjoy I mean it was interesting to watch the number of retries someone was willing to do on each level to get that minimum turn count for no reward. 😲

If there were no rewards, there would be no motivation, and no one would do it. It therefore follows, there are rewards. Challenge, boredom and, as mentioned above, bragging rights. I mean, once you have beaten a boss or a level for the umpteenth time, what's left? 

Move onto other content?

Though I readily admit that is just wasting time differently... welcome to mobile gaming!

The outside world? Sunshine? Time off the phone? :D :D

But, I guess I can't forget this Greg Glassman qoute I saw in a gym once....

i

XD XD

Sunshine? As a vampire, I find that highly offensive.

i

Better for points than for nothing.😜