Gonna play a bit of devil's advocate, think of a popular MMO like an amusement park, selling a service that several people are using at once, a service that has a certain capacity, and that the quality of that service tends to degrade the more full that capacity is. Long wait times in lines, crowded, noisy, messy. MMO's have the same problems, and emphatically more at expansion launch.
Both services are also focused on immersion, and experiences are much improved when it's not crowded. An early access pass for an amusement park has to be prohibitively expensive or limited to achieve a good experience.
Blizzard's shit, but if FF14 did something like this I'd probably go for it.
Amusement parks can't just spin up extra servers to handle load at peak times. Video games can. Also there is not a complex economy and ranking system that pits guests against each other at an amusement park.
They also need bandwidth infrastructure. Like theres reasons ff14 stopped sales of its new expansion instead of just "spinning up extra servers". Theyre not installing a direct line from your house to their server, data from around the world is converging on data centers through utility data lines.