At some point, businesses may force action.
Hundreds of them, maybe thousands, have already triggered contingency plans. You may have seen the stories in passing of jobs being cut or personnel moved to the EU27, and especially in the financial industry there's a lot of asset transfers going on, with capital flowing out of the UK.
But so far there haven't been any showstopping household names that would make the average person in the street sit up and shout "Woah! Wait a minute. What are we doing?!"
If one of the big car firms, for instance, brings forward its plans and exits the UK market before Brexit Day arrives, that would be something impossible to brush under the carpet.
So the closer and closer we get to 29 March without a resolution, the more other firms are going to stop planning and start acting. All the largest companies already have Brexit contingency plans sorted out, there's no doubt, but as yet only a minority have executed those plans.
And once the trickle of bad news becomes an avalanche, once the dam bursts and firms see their competitors coming forward and saying "We're taking XYZ action", that's when something will have to happen.
If Theresa May runs the clock all the way down to Brexit Day then, even if she revokes Brexit at the last possible minute, we will see the ripples of that dithering and can-kicking spread throughout the economy.