They haven't banned 'em entirely, but they have kept 'em from taking up nearly all the beach like they used to do in some spots. Especially on eroded beaches where the sand strips are narrow, the old situation would leave much of the space occupied, degrading the experience and ceding only the last few feet to the waterline. It's a bit like the old situation on sidewalks...lots of encroachment on what's supposed to be public space by private entities, to the point where you had to walk in the road because sidewalks are too jammed and impassible.

As for the food and other vendors, there's no on/off switch for that. The operators of the chair sections generally only get you drinks when called and settle up at the end, but everyone else (i.e. walking vendors selling food and all manner of physical items) don't operate that way and you have to say no thanks a lot.