There's no one answer
People work different schedules, the schedule I personally work has me working slightly more hours than average overall but I have more days off, so I'm free on a lot of weekdays, other people have more flexible schedules or work nights or weekends
Some people have PTO they can use, some have cool bosses who will just let them take time off whenever they want to, some people are those cool bosses or are self-employed and can set their own schedule
Some people are unemployed, some are retired (I've seen a lot of older folks at some protests near me)
Others are financially secure enough to be able to take the hit and think little to nothing of it
Others make sacrifices in order to make it work (if I had to take off without pay, I'd be out a few hundred bucks, it would hurt but I wouldn't be ruined for it, I might have to skip out on a few things I'd like to do, maybe cut some corners and buy cheaper groceries, cancel a subscription or two, borrow a couple bucks from friends or family, put a couple things on my credit card to pay off later that I otherwise might have paid for outright, or maybe work some overtime before or after it to make up the difference, but nothing I couldn't recover from fairly quickly.)
And with some exceptions, not everyone is going to every protest, some may only make it to a couple, some may make it to all or most of them, some may not be able to make it to any but may find other ways to help