I think the majority of people don't care, or at least not enough to do anything about it.
Consider this though, just because someone "knows" it is right, or better, or whatever does not mean they will do it.
Look at some of the things people "know" for a fact they should either not do or change in their own lives yet they do not do it even when it is beneficial to themselves to do so. We can not always logic our way out of something we did not logic our way into. Things like diet, exercise, smoking, relationships, etc. These are all things that many people "know" they need to change and yet they often do not.
Why don't they? You are correct that sometimes they do not care enough, sometimes they do not want the inconvenience of trying but these are not the only reasons either. Just the figures about what americans spend each year on their pets (that for pets not the pets themselves) help to show that people care about animals. But trying to overcome thousands of years of belief that a cow is meant for eating is hard to do and can be frustrating and can seem like people do not care. Try to imagine if someone was asking you to believe the opposite of what you believe now? That you should be that way towards animals after you have been told forever the opposite.
I think people care but it is a different and sometimes confusing path to go down when all your life you have done something different and change is not always that easy.
An example I sometimes use is this. Most adults can tie their shoes without even looking at them. For the next week tie your shoes the opposite way of how you do them now and see how well you are doing at the end of the week.
Sounds quirky I know, but it helps to show how even though you may "know", there is a big difference between knowing and doing sometimes and the doing, even of something as simple as this, can be different than what it seems before you actually do it.
And going vegan can be harder than it seems. It is not just about not eating meat, it is about, what do I cook, where do I buy it, is it more expensive, is it healthy, does my small town store have the products, and on and on.
I am not trying to be critical of you Maise with my post but rather trying to explain why it may seem like so many do not care. You are someone who has already made it there while others do not even believe in the path let alone know that the path exists or how to walk it.