I don’t see what your point is… this isn’t an either or thing.

It’s not literally milk, but these are clearly milk substitutes, where people use them when they would otherwise use milk.

There is a death spiral that can occur when demand for dairy milk declines below a level where the supply chain can no longer support itself economically. Milk consumption is down 40% from the 70s in the US, 2730 dairy farms went out of business between 2018 and 2020, and if I had to hazard a guess, younger folks are going to prefer non dairy alternatives (for a variety of reasons).

https://www.theguardian.com/food/2020/jan/06/us-dairy-indust...

And how many people are those "some people?" If it's less than 100% of all current milk drinkers, there is some benefit to be had, and the more people that are comfortable with milk substitutes more often, the greater that benefit. The point is to reduce greenhouse gas emissions, not get to 0, which isn't possible with milk alternatives either.

Saying you will never give up something regardless of the costs is the definition of being unreasonable