I'm the modern age where gaming has become more mainstream, it's very, very rare for games to sellout (mostly for unexpected major successes on nintendo's gaming platforms), especially big name yearly releases like CoD, and even then, we live in an age where anything can be downloaded given time, so the supply truly is limitless. The whole point of early access games is that you're taking a risk by buying into them (generally at a reduced price compared to a normal game) to test for them and help out the devs, so at least the cost is Lower and they're warning you. Physical copies of games are still the majority on consoles, however, and the low level of the data storage size at launch of ps4/xbone and the reduced speed of downloads compared to steam don't help either. It all comes down to the waiting game for digital downloads to take to the majority.