Starbucks did what you’re suggesting to increase turnover and profit at stores — but the opposite happened: sales dramatically dropped, even though the time to serve a single customer and the average customer stay both dropped.
The issue is that Starbucks doesn’t just sell coffee — they’re a cafe. And cafes are in the business of selling thirdspace, where you create fun memories with friends and family. So when they provided a substantially worse version of that product, it sullied their brand and lowered their overall profit, because people no longer associated coffee at their chain with good times.
Similarly, the owner of a small cafe I used to work from loved the three or four regulars who would come near open and stay all morning — us being visibly chatty in the large storefront windows would draw in more of the nearby joggers than if the store was empty. We were a free living ad that getting coffee there was a fun time and popular with locals.
I think you’re ignoring a lot of ecosystem complexity with your “optimization”.