I just don't understand

Our neighbors to the left kept their air conditioner in their window all winter. For the last two days, they've had it running nonstop.

When I walked outside today, I noticed the neighbors downstairs have their a/c installed and running as well.

It's been a beautiful upper 60s/lower 70s for the last week or so. It's gorgeous outside. It's refreshingly comfortable inside with the windows open and the ceiling fans on low.

Why drag out the a/c now? Summer will be long and humid enough -- I'd rather not live like it's summer for any longer than I have to.