In comparison with the world, a relatively low percentage of people in Finland is lactose intolerant.
https://worldpopulationreview.com/co...nce-by-country

So the argument it is easier sounds right to me. There is no real reason to not serve common milk. The idea is that they go by the lowest common denominator, so if everyone can drink the substitue without issues, they only serve the substitute.

Personally I think they should do both kinds. The lactose-free often is sweeter, which isn't a good thing in my view. And it can't be that much of a bother to keep both, but it probably saves a few penni ...