[eridius]

If you use up your combined PTO on vacation, you don't have any left when you actually get sick.

If you hoard your PTO in case you get sick, you don't get to enjoy vacations.

There's a middle ground, but the spot where you draw the line and say "I need to save this many days in case I get sick" is going to be different for everyone, and most people are not going to calculate it correctly.

Not to mention the employee isn't incentivized properly here. The employee that takes too much vacation and goes to work sick, they're not the one who pays the cost of them going to work sick, it's the other employees who do. So a combined PTO scheme like this actually incentivizes employees to err on the side of taking more of it as vacation than they should.

[ghaff]

People can typically borrow against future PTO if they get sick and don't have time banked. Again, I don't advocate a combined system and I actually agree the incentives are mostly wrong (for everyone except those who abuse sick time when they're tracked separately which are probably less common among readers here than in the general population).