Usually depends on which state you are in. California I believe they are required to pay up to a certain number of hours.

(not a lawyer) I think in the US (oops, probably should have said California) generally accrued vacation has to be paid off (as it is accounted for at the time it is earned, but there may also be a cap which causes some to disappear). But sick days are not generally considered a benefit and avoid this. I imagine "flex time" is more complicated.

In most states, that's not required.

My employer will not pay us for accrued leave. I saw the end result recently when a co-worker took a week and a half off only to return with his resignation in hand. Guess he cashed out his vacation time anyway....

Now we all realize that if someone is going to resign, it's most likely going to happen after a long vacation. I don't know if HR realizes this yet.

In CA leave is vested, it has to be paid out. Not all states have this policy.

My last two places were like this. I can't say I was happy about changing, but I can say I priced it into the equation.

We always hear this, but it doesn't really make sense. First, a firm that actually wanted employees to take vacation could just make a policy by which a certain percentage of banked time would be automatically scheduled by HR after so long a period of banking. Second, under the "lose-it" policy, many employees don't actually use all their allotted vacation. This can happen even to those who really try to schedule it. A cynical manager can always stymie the best-considered vacation plans. I consider that this common result is actually the intent of this anti-employee policy. (At many firms; of course any particular firm may be an exception.)

No, it is so the employer doesn't need to carry the additional liability in their accounting. Vacation time is something with a monetary value that must be paid out if the employee is terminated.