Many employers believe that your obligation towards them doesn’t end just because you leave.
Annoying that it is, sometimes they are right (in the legal sense, at least), and there are certain clauses in the contract that have to be fulfilled before you are allowed a taste of freedom. Other times, they are just seeing how long they can still exploit you before you put your foot down and tell them that this is not going to happen anymore.
However, when you have been beholden to some corporate overlord for lord knows how many years, it can be difficult to differentiate for yourself what is acceptable behavior when you leave and what isn’t. Some workplaces get a kick out of making the resignation experience a total headache, adding complications where there really doesn’t seem to be a need.
The most important thing an employee can do when they are planning to leave a company is to make sure that they go over their contract and check that there aren’t any awkward clauses that may work against them further down the line. These tricks are more common than people like to think, and it goes without saying that they can be very stressful.