Animations are the little visual effects of closing an app, opening an app, swiping from one screen to the next, etc. They're supposed to be extremely subtle and make the phone seem to have more of a flow to it. I think they are good to a degree, so I don't turn them completely off like some do. I leave them at 0.5. But to leave them at the full 1.0 is ridiculous in my opinion. Apps do need time to load, but if the phone is using part of the processor to complete the animation instead of loading the app, you'll wait longer in my experience. With the animations toned down to 0.5, that seems to be the perfect balance.
It actually serves a pretty big benefit to doing this, because ever since my S3 when I did this, Samsung devices are much faster and smoother. I had a good deal of lag on my Note 4 and when I limited it to 0.5x on animations, it has picked up immensely and the lag is ALMOST gone. The appearance is most definitely personal preference, but the actual performance is not just "thinking it helps" as it is pretty obvious that it does and would be easy to test if I had the right set up to do so.