The only way this could work is if they charged people a refundable entrance fee of like $1000 or something. Otherwise I could see it turning into a squatted living space with druggies hanging out getting in the way of potential customers. Or posing health risks to customers (needles in cushions, unsanitary personal hygiene, etc.)
I guess you'll be shocked to hear that shops with furnishings inside of them (including, but not limited to the Macy's department store) have been operating for decades without installing anti-homeless spikes on the floor samples, _or_ charging an entrance fee.
Having a human posted at the entrance whose job is to bounce away hobos is (based on my personal, first-hand observations) more than sufficiently effective.
You (intentionally?) missed the part where hobos get bounced out at the front door.
You've also pretty clearly not been in either of the Macy's buildings. [0] They, -too- (just like the other large department stores that have been operating in the area for decades) are so large that the employees on the floor cannot see what's going on across the entire floor with a glance.
[0] Well, they _used_ to have two. Since a year or two ago, they closed their menswear building and consolidated in a single building.
This issue is a new issue --it's not decades long. It's only become an issue since intersection of prop 47 with SF governance. This is why companies are only beginning to pull out now.
Unbelievably, SF already had loitering and vagrancy laws on the books, but the panhandle had to have a new more specific ordinance to address druggies blocking doorway entrances etc (the sit/lie law), of course, in typical fashion, it could only be enforced after a written warning and after a second it became a misdemeanor...
It's just easier and better to find a place that's friendlier to business.
Sit/lie in SF is from 2010, ~13 years ago.
SF has been in a commercial decline for a whole bunch of reasons.
Despite that, front-door bouncers have continued to be -as far as I could tell, as a customer of these establishments- more-or-less totally effective at keeping hobos out.