He doesn't tend to show up in the lists because he pays himself relatively little (compared to other billionaires). Between 2014-18 he had income of $125m, and paid tax of $23.7m[1]. That's still lower than the average American absolute tax rate, but way higher than most other billionaires. So he's a bit less of a sensational headline than his contemporaries.

His wealth growth of $24.3bn is untaxed through those years, he presumably left those assets in Berkshire Hathaway where he'd personally not generate a tax bill for them. Eventually Buffet, or more likely his inheritors, will sell the Berkshire Hathaway assets, and should pay a monumental tax bill on them.

[1] https://www.propublica.org/article/the-secret-irs-files-trov...

Why would they ever sell anything when they can just use them as collateral for loans and avoid ever paying taxes.

How is that inconsistent?

Because the narrative being developed around him is that he is such a selfless guy, humble midwestern values, wants good for America, yet he structures his affairs in a way that he pays as little tax as possible and would be largely unaffected by increased income tax...

From my understanding, his income would be from capital gains, and he does advocate for increasing capital gains tax rates.