Because it is a pretty weak ending to a series. I also know what will happen, they will have a barn storming first episode with maybe those blue armour wearing dudes arriving en masse on horseback, Negan and a bunch of others will escape. The episode will end up with the rest of the group pulling sad faces around the grave of <whoever>, probably Glen, Maggie will probably get better all of a sudden and Carol will rejoin the group. Then they will faf about for a few episodes before another run in with Negan for some pay back just before the mid-season break. Its getting a little tiring really because it really is a great show.