Migrations are often a point of contention between communities, so we are very conservative when it comes to adding default migration paths. In essence, a site would need to show a history of successful migrations before a new default can be added. (Yes, this is a bit of a Catch-22 since you'll need a moderator's help to migrate to a site not on the default migration path.)
In the past 90 days, there have been 3 migrations to Academia and one of those was rejected. Compared to the current defaults (Mathematics—140 migrations; 10 rejected and Statistics—10 migrations; 1 rejected) there's not a lot of evidence for this migration path.
So for the moment, I won't be adding a migration path. But we can look again if there are more migrations to Academia in the future.