Why rush Sheldon and Amy to relationship milestones when there are still laughs to be had while they’re adjusting to cohabitation?
Given how Sheldon and Amy have been shown as the ideal mates for each other, we can probably count on The Big Bang Theory intending that Shamy will be a romantic endgame.
Amy may want Shelton to commit to hooking up more often than on her birthday if she’s going to want to marry him.
Besides, coitus is still a relatively rare occurrence for Shamy.