I work from home and have flex time. As long as I work 40hrs a week between sunday-saturday of the following week, I can work whenever or however I want. Like I can work 6am till noon, clock out and return to work 7pm-9pm. Whatever. When you enjoy that kind of freedom, you never really need a mental or sick day. I bank 3-4 weeks every year (rolls over, 500hr max limit), take 6 weeks of vacation May-August, and the occasional 3-4 day weekend here or there. But because of the flex time, I would rather work 4 10hr shifts from Mon-Thursday, take Fri-Mon off, and then work the following Tues-Fri 4 10hr shifts. I get the 4 day weekend, but don't have to use PTO that way. My job is mentally exhausting though, so I do not like doing 10hr shifts and often just use the PTO anyway.
If I'm not really feeling like working that day, I just don't and instead work the hours another day. I generally work Mon-Fri by choice and because I like to have my weekends free. Flex time is an amazing perk, especially while raising kids.