Why can't bars sell their in house brewed beers? We've got this local bar that brews their own beer but when I tried to buy a bottle to take home they said they were only allowed to serve the in house beer, not sell it. If the state of Florida issued them a liquor license to serve and sell beer, why can't they sell what they make?

Just to be clear by sell I mean sell me a bottle and let me walk out with it.
Most States have two different types of liquor licenses.  On premise and Off premise.  On premise is selling alcohol to drink there, off premise is for taking stuff home.  It is entirely possible that an establishment will only have one or the other.