I have a one-square level in my design where the player looks down from a very high building. I even used the multiple-vanishing-points approach there.
A good reason for another perspective would be that the player is e.g. sitting inside a mecha and looking down on a village...
Or sitting on the back/head of a dragon...
Concerning the horizon: something which is not very far away would certainly be affected, e.g. a forest in the background that covers the horizon should probably be moved some pixels downwards.