Cuz you only need 1 to stall (will stalemate 1v1s and prob most 2v1s on the payload) and the early exp/doubling of the payload is bountiful. Kinda like bhb, early turn-ins are a waste and level advantages mean you can do w/e u want or towers where early caps mean very little. I predict that early siege stuff that u see on most 2 lane maps will come out in full force for this map and that the extended value for mercs and keeps on top of the slow ass push of the payload will result in minimal resources spent on pushing the early payload. For ex. if you do sylv or hammer comp (oh god hammer will be strong on this map) and take the early keep and the other team either responds or tries to do the payload, you are pretty much running the game. Early building means you are gonna double the payload you gave up (you dont even have to give it up since it's easy to stop) and you are gonna be up a talent tier, so like bhb style you are going to own the map. It's fine to push a payload through the lane cuz you can soak at the same time, like that's a worthy use of resources, but once you get out of exp range it doesnt feel nearly as important as say taking a camp or getting soak/sieging
Conversely it could also end up like this: 3 ppl on each team dedicated to the payloads in order to race boe style w/ 2 in either lane and rotating in and out as appropriate. I only played one game, but i kinda feel like the map is too large for this (tho globals exist)