On why some people are inconsiderate toward other people

"People who refuse to EVER be considerate of other people and other people’s feelings, why?"

Maybe there comes a point in the most considerate person's life, when he/she reaches his/her limit of being as such; When everyone just ceases to respect him/her just because he/she is always there, nice, understanding, helping whenever needed.. By forgiving them time after time, a person teaches other people that it is ok not to care about his/her feelings.
Much like people treat their parents, who have been nothing but unselfish: with hostility, just because they can; It's safe to do so (BTW That's why bullies bully the weak and in numbers; it's safe), it's ok to treat them badly, because you don't have to consider them, you don't have to treat them with respect, like you would with an equal person, because you think they are less, whether you admit it or not. After you lose people or spend time apart you might see what their true value was, but not before. Rarity, limited access and supply increase value.

When something comes abundant, secure, for granted, without a price, people stop noticing it, respecting it. In the mind it becomes less valuable. I mean I bet none of here us wake up being grateful for being able to breathe, because breathable air is always there, it's abundant, it really asks nothing in return, so how to do we treat it: not giving a shit, it'll be there. We don't even think about it, that's how much we care.

When time and time again people prove to be as mentioned before one might come to the conclusion: No point being nice, since you just end up being used and neglected, and since you carry "the niceness" in you, it allows others to be more asshole-ish. It's like carrying a coffin or something together, if a few do more, the others can slack off at their expense. But once that is gone, people learn to miss it, you can't miss something that is always there. Drop the weight, let others carry it, only then they'll learn to value the contribution of others.

In other words: being an asshole is a necessary evil. It reminds people to be nice to each other, because meeting an asshole feels like shit. Then people might ask "Is this something we want, yes / no?" But they don't consider it before that, because they don't have to. Assholes are very necessary.

TL;DR: It's better to be an asshole yourself, than let someone else do it: at least you can do it right and with style.

I've said this before but: What I have learned from my time on this planet is that respect DOESN'T go both ways, it only goes up. i.e. if you respect someone, you present yourself to be lower value / inferior.

If you stop respecting people, they start respecting you, as backwards as that might seem. And the respect multiplies at least by the factor of 10 if you don't respect them even that much that you let them know that you don't respect them.

If you don't believe this, then take note who are always the people who get betrayed, stabbed in the back, who get publicly shamed and crucified, who get shat on, who get burned at the stake. I tell you, it's not the assholes, no one wants to cross them, and people usually secretly admire them for being an asshole; It's the ones who say sorry and admit doing wrong. Meanwhile the ones who blatantly say "I'm not sorry, I did it because I don't give a shit about you." always seem to get a pass.