Seagull of Rage
The Destroyer
I thought about this much more than I reasonably should have, and I still can't see any positive effects. All I can see is a minuscule fix, and a lot of negative side effects.Well, I think that this would affect more than what you might think at first glance. I believe there are more positive consequences than you might realize if you only consider, "Oh, I have no problem with zombies on my roofs, so this wouldn't affect me at all."
They are invading. They should reasonably be able to scale a wall. Also, this logically falls apart considering the fact that they have flying ships.In the next trailer, there will be a segment where they defend a pirate invasion from a large castle. We see pirates struggling to climb the castle walls, with flying parrots being the first to arrive! Eventually, the flying ship arrives, and chaos ensues as pirates start jumping down from the ship.
As long as the player actually has protections in place, they should be fine without this suggestion.There will also be a segment where they relax by bathing in bubbling bathtubs on a balcony in a large building in the snow biome during hardmode, as no common enemies are able to reach them up there.
Conclusion: I feel like you aren't thinking this through enough. Besides the issues with this not really being a needed change, it would also allow for a lot of cheesing, as you could just block enemies from spawning by building a wall, and not even having to worry about it. Enemies randomly attacking you is part of the experience, and one of the reason I love terraria.