I'm someone else grew up on a relatively rough, tough, deprived council estate (big northern city). Likewise, no contacts, help, etc., etc. Married someone from another council estate in another northern city.
We were both lucky enough to be born clever. So, we went to university, had a good time. (That's when we met.) Travelled the world. Got jobs we enjoyed. Made money gambling on various stock exchanges/financial markets (easy when you know how, perhaps lucky there too (though I suspect not)), enough to set our children up and to not have to work for pay any more. Settled down in a nice house in a nice suburb; children scattered here and there, decent lives all.
Of course I didn't deserve my nice life and lots of money. I was just lucky. Like you, @Thequiveringpossum. And we ought to contribute to society, to other less fortunate people, whether they slag us off or not. We did that in our jobs, for a bit, but that's really not enough.
No-one says you did anything wrong. You were just fortunate to be born the way you are, hard-working and all the rest. Did I do anything wrong? No. (Certainly nothing illegal!) I was just lucky, like you.
Why should you (and I) contribute? You ask. --Because it's the right thing to do. Morality, if you like. Or just call it fairness. You and I both should pay high taxes ... or, failing that, and while we wait for our fellow citizens to see this and make the democratic choice so we have to, we should contribute via charitable donations to help those less fortunate than us. Of course it'd be better to pay tax. But, well, ...
It's only fair.