They are taste very differently and every time I try to make baked foods with substitute milk something is wrong. Lab meat has appeal because is the exact same.
Also, people with ethical concerns about killing cows > people with ethical concerns about drinking their milk
I don't act much on my moral convictions, but generally I'm anti-torturing farm animals. The lives of beef cows seem way, way better than the lives of dairy cows.
Drinking cows’ milk at any scale requires killing cows, though possibly people are less aware of this.