I don't really understands why it's like this… Is that deliberate? if so please give me a reason why players are allowed to summon their mount instanly?
The issue actually is the obvious escaping exploit, people are griefing, ninja looting, training with mobs, or going through full dungeon with no issue, by just instanly summoning theie mount wwhile flying to ride and dash.
Summoning a mount should require to be OUT OF COMBAT and takes at LEAST 2 seconds casting time.
This would negate most exploit and give actual purpose to the dismount option instead of unsummoning option.