My guess, because Bioware were more concerned with making this: https://www.ea.com/games/anthem Which looks visually stunning. I'm reserving judgement on the actual game till we know a lot more, but the polish on this thing is amazing.
I reckon being that Mass Effect is a pre-existing IP with a lot of guaranteed sales, established clientele and that, Bioware put the "B" team on Andromeda development, to give newer and upcoming devs within the company more experience developing a AAA game.
Just a lightbulb thought I had whilst watching e3.
Kind of intrigued by Anthem.. if a little cautious.