If people are naturally selfish and they’re giving you advice to not be selfish, why aren’t they taking their own advice? And why should you take theirs?
It’s like a burglar telling you it’s a good idea to leave your doors unlocked.
Lots of people act, at least partially, in unselfish ways.
Selfishness is not a binary characteristic. There are degrees of selfishness - and spheres of selfishness.
Just because something is in our nature, it does not mean we have to behave that way all the time. Most people are neither purely selfish, nor purely unselfish.
To answer your question though, since selfishness exists on a scale, your assumption that people offering advice are not also practicing it is, at best, a conclusion without data.
fwiw I agree with you on these gripes, tech bros are often selfish, its something I really hate about our industry and I'm struggling a lot trying to find a software job that does good in the world because mine doesn't and it makes me feel awful, but I am trying at least.
And anyone living an unsustainable lifestyle (almost everyone) is selfish though its such a huge problem that putting the blame on any individual feels wrong.
I think where we disagree is that you're so all or nothing with this. People can be selfish in some ways and not others. You can live unsustainably while also having principles in other ways. Things could always be worse. I encourage anyone to care about the world as much as you can without being self destructive about it, and I really try to live that way myself.
It’s like a burglar telling you it’s a good idea to leave your doors unlocked.