Blizzard’s history with merging realms and properly handling low population servers is awful. Years ago they said that they were going to merge every low population Modern realm in the world to a significantly higher population, they didn’t. They even closed the thread and tweeted that merges were done. That was two years ago and we haven’t even been given an update since then.
It takes Blizzard years to merge servers and they do a conservative, terrible job. This is Blizzard’s fault that no one wants to take free transfers and risk being on a dead server that Blizzard doesn’t do anything about.
Here is my thread on their failure to complete their stated goal and the lack of communication after they failed: