because 2.0 is basically a freebie, sort of a bonus only available to impulse
because SDC is a heavily patched application which would require additional updates to support the 2.0 update and all the new galciv2 versions (UL, EU ...)
stardock team is also encouraging players to contact support/forums for sorting out their problems with impulse
I guess it could be understood as a way to encourage players to move to impulse from SDC, since SDC will be dropped overtime
for more info : https://forums.stardock.com/329125 every answer is there