Your friend is probably like mine, and spends less time going from table to table and in crammed kitchens and dish pits than his staff. Maybe he is a bit older and spends less time partying and shit. It's all about exposure and viral load. He'll get it at some point, and be worse off than if he'd been vaccinated, it's pretty much that simple.
What's really ironic is restauranteurs being so vehemently against any form of restrictions early on, but now they will likely be forced into self induced shut downs for their busy season for X years to come. They will have permanently lost a portion of customers who will never really feel comfortable going, and have adapted their life style already.
I don't think people understand what a seasonal "endemic" virus with crazy r0 and immune waning/evasion will look like (it looks like what we're going through right now). Ironic would be the only thing propelling his biz out of this cycle long term is more advanced vaccine/bio tech. The virus gives zero fucks if people are tired of it and cares nothing for their "lines". It'll just make them sick over and over and over again, probably with very detrimental effects to long term health and economy.