Using a lobster tank in a grocery store as a source for having lobster at home

I’m sure the grocery store that I go to has a rule against this but does it make more sense to just take a lobster from the tank and not pay for it and eat it at home then to just pay for one? Even if there’s a rule I can’t see them IDing me from the security cameras and thought I’m sure that the grocery store would never admit to it I’m sure we’ve all had a lobster at one point and that the grocery store decides to skip a lobster and use the moneys that they would have spent on it on things like stupid rules that don’t really stop things from happening. Just a thought