There's no hard and fast rules. No, a company will never retroactively pay for you learning, but yes a number of companies will reimburse you if you attend graduate programs while employed with them.

It's a balancing act. If a company wants employees to keep learning, they need to invest in that. If I, as a salaried employee, am expected to be available outside of the explicit working hours for emergencies, then it's also fair that I be allowed to do things that are directed at my own career during work, bonus if it proves useful to the company.