I mean that's the other issue. If it's a use it or lose it type deal, of course people are going to use every possible day they can, hence why most companies tie vacation, personal, sick into one giant block of PTO and you use it how you need to.
The problem with that though, is that you have people who keep a buffer of days to use towards the end of the year when the weather gets colder, etc for them potentially being sick, and then when it doesn't happen, you have everyone trying to take time off at once the last two weeks of the year. From someone who used to manage people, and do the schedule, that was the worst time of the year because you still have a business to run.
Having everything as one block also leads to people coming into work when they aren't feeling great, so they don't waste their vacation time, then getting everyone else sick in the process.
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