Why nobody builds Zz'Rot
It's useless early game. Without the extra damage from built armor or MR, you aren't going to get a whole lot done with it. There are just better places to spend your gold for your first couple of items.
Mid game: tanks split pushing just doesn't work. You can't 1v1 anybody, and, for most tanks, don't have the mobility to escape when someone comes to counter you. Your time is better spent with the team then trying to slowly push down a tower. And you can't just drop a portal and leave because the voidspawns will almost never reach the tower
Late game: By this point, most of the towers should be down. Either your team is winning, in which case you don't have many options for where to splitpush and your team is going to want you for fights anyway. OR your team is losing, in which case you won't even get the chance to extend to a tower without dying in the process.
Also, the voidspawns just die. Like, they feel like they do nothing even when they rarely live. It just feels like a uselss item when they never get to the tower. I wish they ignored minions, or had more health, or didn't die after only 5 seconds on the field (mostly this one).
See?
(probably not optimal anyway but i'm just illustrating a point)

as random examples.
Tanks Don't Split Push ??? [ My Life has Been All A Lie !]
