It is just time. I love to take a gym fast, expecially now, in winter, just because my hands get cold during long battles.
Before Gym-Reward-Update, there was another point:
Taking down a level-10-gym with 6 PKM was quite a challenge. So it was fine to have strong attackers.
Now, it is not as urgent as it used to be, for two reasons: The reward to clear gym completely was taken down, and there are much less level-10-gyms.
So your point of view seams quite reasonable to me.
I still power up, to PKM-level 30, what seems to be a good price-performance-ratio.