It's a quick and easy way to dramatically increase their user base.
At the moment nobody can complete with Steam because Steam has most of their games. If there would be a way to transfer games between services, services would have to compete and what services they offer instead of just relying on user lock-in.
That might not be up for Steam to decide, first-sale doctrine already exist as law in many countries, what's missing is the enforcement of it for digital goods:
At the moment nobody can complete with Steam because Steam has most of their games. If there would be a way to transfer games between services, services would have to compete and what services they offer instead of just relying on user lock-in.