Any reason to power up high Def monster ? Steelix , umbreon ??

(1) Just for fun and surprise. I put them in a gym i do not expect to last for long time.
(2) Power up until in good range to prestige. Those Def-Monsters are Star-Prestigers.

With the increase in players a lot of my local gyms start at around 2000 CP so 2100-2200 defenders are relevant - bottom half of gym, but sometimes 2 or 3 defenders below them. Steelix is a pretty decent defender if you get it off the bottom.