For extremely busy restaurants / cafe's where people are already waiting long periods, they probably don't want to overcomplicate things too, and increase the risk . They'd have to keep 2 different milk frothing machines, and every time a customer got sick, risk getting sued, whilst slowing down the efficiency of orders.
Whilst it might increase the number of potential customers, in practice, it might only have negatives
Last I checked, it was more like 6-8% for UK.. So, 6-8 out of 100 customers in that case would slow down everyone's orders, would reduce the efficiency, increase the business risk and also require a whole bunch of extra procedures to avoid "poisoning" someone. If they're already overbusy, it's just costing money.
In practice, Lactose intolerant also doesn't mean what you think it does. It simply means they have some kind of negative reaction, and many people are lactose intolerant to a certain degree if you drink enough milk and eat enough cheese. I suspect I am somewhat dairy intolerant, and I still drink milk fairly regularly.. So, if those 6-8 percent who are actually considered intolerant, most of them probably don't care..
Most people who are considered lactose intolerant can still ingest milk in their coffee though, because its a small amount with no impact. They're not deathly allergic.. Some of them likely also take Enzymes to allow them to digest dairy.
So, if we're talking ACTUAL numbers who this affects, its fuck all really, except the ones who are genuinely allergic (and do you really want to be serving hundreds of drinks an hour which look EXACTLY the same to customers who might get seriously sick and sue?)
Disregarding that, the cafe has clearly calculated the business case, and determined serving oatmilk just isn't worth it..
Also, I have noticed at least 1 person in this post repeating brand names, so i almost wonder if some viral marketing is happening here..
I don't drink coffee though (it tastes like dogs arse), so I don't really care though to be honest. And I don't work in a cafe. The only info I'm working off is off people I know with IBS and dairy intolerance.
On the other hand, oat milk can be contaminated with gluten too. So, some people who are affected by Dairy, may also be affected by Oat milk too anyway..