we still have this weird cultural mindset that we think we have to give some reason/justification for not going in on a day off. fuck that, just say NOPE

personally i ignore work msg on days off. eventually they get the point that you might as well not exist to them if you're not currently on the clock

Yes, zero reason to respond to work if you're an hourly employee and you're OFF the clock.

Unless they pay you specifically for being available.

I know what "on call" means.