Do people want them to try and canonize an ending? Or try to work with the mess that was ME3's finale?
This is better. Fresh characters, setting with the same familiar races and universe we love. This is actually exactly what I hoped for. Basically a reboot without being a reboot
I can only speak for myself, but:
1) Because galactic travel shouldn't be possible. It would take centuries for a ship to even cross the gulf between the galaxies, let alone find a garden world (that's not already occupied). And without a way to discharge a drive core periodically, a ship will fry itself and the crew long before that happens.
2) Because if galactic travel was possible, there is absolutely no reason not to think the Reapers have gone there as well. And so we'd be stuck with harvested cycles, Crucibles, and ME3 endings.
3) Because it is painfully obvious why we are relocating to Andromeda. A terrible, terrible ending that frakked with the entire galaxy and Bioware is too proud to backtrack on it. So the only answer left is permanent exile from a galaxy containing 300 billion stars which it is feasible to reach given mass effect technology.
4) Because it's abandoning the familiar touchstones of the precious games: The Council, the Citadel, the mass relay network. And so on. I looked at the trailer, and I didn't see Mass Effect, I saw a scifi shooter. Like any of a dozen others out there. I don't understand why it's even called "Mass Effect"