Probably missed as many days off in the past two decades as I did for all the years up to 25 combined. Not many. Two I can remember were for the winter vomiting bug in around 2014 and the flu in 2022. Both times I literally couldn't leave the bedroom, even getting to the bog was a gargantuan effort.
But I do get 28 days leave per year, somehow with kids it's still not enough but thankfully I work for a guy who is very flexible on working hours so it's never a problem for hospital appointments or kids off sick.
I think the fear for employers is the growing recognition of mental health care means that being signed off for weeks and remaining a protected employee, far outweighs the preemptive move to grant mental health days in advance.
We have a number of employees off currently with various issues and the goal is to get them back well and ready to fight for the business. The issue is there are probably a small minority who will take both, either because they need far more help than a day off here and there, or because they're taking the piss, and the ill feeling it creates in covering for colleagues who are off ill but still posting on Facebook or Instagram about getting bladdered at the Christmas markets or seeing the latest blockbuster movie - all perfectly legitimate if you're trying to get yourself well again mentally, but very inflammatory when seen by colleague who are working extra hours, missing kids nativities etc.
I was toying with the idea of moving to Canada at one point, but I think they are similar to the US in that you get next to nothing for time off and there seems to be a general culture of employer first, family second, hope that's changing a bit though. Met a Canadian couple in cuba a few years back and couldn't believe that they were taking a four day break to the Caribbean and that was nearly half their annual leave.