This is the reason why. You may prefer the world to be a certain way, but you aren't willing to make any sacrifice to make it be a particular way, so it appears that you don't actually care about an opinion that you are espousing.
People who don't eat meat have a net effect on a reduced demand for meat, reducing the amount of cattle. Becoming a vegetarian doesn't stop everyone eating meat, but it helps.
[I'm not a vegetarian but I have some respect for people who are willing to stand by their beliefs]
For me, I see the greatest impact I can personally make as continuing to work to become successful and then investing a ton of money into lab-grown meat.
Anyway, it's something I'd like to help do something about, but it's not my life's focus. If I had a magic "make everyone stop eating meat" button, I'd be tempted to press it and figure out a way to personally adapt, but ultimately I think that would cause more harm than good without a market-ready drop-in replacement that fits the same macros. That's not the same as not caring or being unwilling to make a sacrifice; it's just caring about multiple things to varying degrees and being realistic.
Says who? OP is willing to make a sacrifice that results in desired effect - just not "any" sacrifice, which in this case does nothing.
If I think taxes should be lower, should I start paying less tax then I am asked to?
For example, say that we have genuinely useful medical information as a result of Unit 731 experiments and similar crimes (which may or may not be the case; I have no idea). There's no contradiction if one person supports using those existing results to save lives while simultaneously opposing further collection of such results.
Another example: I personally eat a lot of meat (keto/LCHF), but even so I might support legislation to ban killing animals for food or sport, because the personal sacrifice would only be worth it to me if it came attached to a systemic change.