Someone did something at Sonic to make them issue the statement though I agree with your statement.
For people on foot or wish to park their car off-property, some Sonics have an order-radio in front, perhaps a table too. This is about the only place I would see such an interaction. Doesn’t make much sense if it were people who had guns in their cars.
Sonic has begun to build some facilities with indoor seating. Google images shows a few