The Reason They Like Mountains · 2:34am Jan 21st, 2019
I've heard a variety of possible reasons why unicorns like mountains, from the physical ("lots of gems there") to the psychological ("Rincewind Arcology Syndrome").
Well, on a pragmatic note, seems to me that it would be an excellent defense, inasmuch as there is an excellent defense, against Commander Hurricane's Favorite Tactic (tm). Namely, loading up the eponymous weather system with a storm herd or two, then riding it back and forth across your country (while, in my headcanon at least, singing the Ride of the Valkyries with great gusto), until either you surrender, or future generations of ponies will be talking about your low-lying and coastal regions in the same way as humans speak of Atlantis and Lemuria.
...it didn't take long to figure out that a really good place to be was (a) at altitude, and (b) on not-readily-wash-awayable stone.
I'm personally a big fan of the Rincewind Arcology Syndrome angle.
But the obdurate stone at altitude idea also has a great deal of merit to it.
Even a minor hilltop has a great deal of resistance to flooding.
I really like how I have trouble telling whether you're referring to the pegasi or the weather systems when you say "storm herd." Of course, card games carry some blame there.
That said, there does seem to be an argument for Rincewind Arcology Syndrome. The fact that Canterlot's modern population density requires many homes to build tall rather than wide may be seen as a feature rather than a bug.