It's because it isn't really something that is supposed to be very impactful on an individual basis.

The trend to push for people trying to eat less meat instead of no meat is because the majority of the population is unwilling currently to give up meat entirely, and are deciding on no changes to their diet when petitioned to try being vegetarian or vegan. But, if you can get most people to eat just less meat, there is a collective impact to the meat industry, and as a bonus, someone who has already agreed to reduce the meat in their diet is easier to convince to cut more meat than someone who has never agreed to change their diet at all.