Along with the previously mentioned reasons, booths also have traffic on only one side of them, vs a table that has traffic on all four, which means more interruptions, more having to move for other people, and more chance of having food/drink dropped on you 
Additionally, for people with certain disabilities a booth allows them to stretch out to relive pain and not stand out as much for people to stare/point at, as well as settle a service animal thanks to the aforementioned extra privacy and reduced foot traffic.

Additionally, for people with certain disabilities a booth allows them to stretch out to relive pain and not stand out as much for people to stare/point at, as well as settle a service animal thanks to the aforementioned extra privacy and reduced foot traffic.