It's not just a US thing. I've never actually thought of this until this post, but I'd think it's because taxes are done annually.
Your employer says they'll give you X amount a year, but you receive X-Y into your account. It's easier to talk about X, then to worry about how Y fluctuates.
It also makes it feel as if you're making more money. Raises for a year sounds better than when you divide by 12 and get the monthly.
Losing Beehaw would definitely hurt Lemmy. This was not my first home on Lemmy, but I quickly saw that all of the good communities seemed to belong to this place.
However, I would probably never have found this place if you weren't federated. I would naively assume others are in the same boat as me.
I did initially come to Lemmy only as an alternative to reddit, but I've stayed because of the ActivityPub protocol. I'd probably not stay active on Beehaw on another protocol, and I'd definitely still keep a Lemmy account on another instance.
I do understand your concerns, and what you wish to achieve. Personally I would have just hoped you tried to achieve it here for longer. Though I do get the struggles with moderation.
Whatever you decide I wish the best for this community in the long term! I hope that regardless of it staying here, or moving elsewhere, it thrives and keeps the content and discussions that its members would like to have.