From my experience, it seems to be a little of that plus a lot of "unusual" behavior from players around the time of release.

Once the game is already out and people are able to log in all the time, a large number of people will only spend a few hours a week in the game. But during release time tons of those people get up early to play ASAP, spend the whole day online, etc. For FFXIV specifically, you get NA and EU players who would rarely ever be on at the same time doubling up. Beyond those people, there are a lot who buy the game to try it out and then decide it's not for them a month in.

Most companies don't want to spend the money on a ton of servers to accommodate all of that, nor do they want to program logon systems which will essentially never get used beyond the first couple of weeks. Not only is there the monetary concern from their side, but if you created all the servers to properly house all the people trying to play at launch, those servers would be veritable ghost towns a few weeks in and you'd have to merge them.

Not that this excuses things like the permanent 3102 or a lack of working queue, etc. in this case.