As you posted, the rules vary (sometimes widely) from state to state re:tax liens. Any research you do needs to be completely state specific. I can tell you how it works in Florida, and I'm sure some of the same principles apply.
First, who doesn't pay their real estate taxes? Answer, not very many people.
What eventually gets sold at auction are abandoned properties, gaps and gores(surveyor mistakes), and low value properties whose taxes exceed the 'percieved' value of the property. Yes, there are properties whose taxes are not paid because of a mistake by the owners. This does happen.
One of the real important issues is that, at least in FL, the taxes have to be three years in arrears in order to foreclose. This is where the 'real money' is to be made and that all the 'gurus' tout. 'You can own properties for pennies on the dollar'. Yes but it will take a while. And the owner can show up on the day of your foreclosure sale, pay the taxes and walk away.
Also, while the lein for taxes to the community is superior to mortgage leins, no matter the date, they are not superior to federal tax liens. Federal tax liens do not automatically attach, but they may and it can be hard to find this out without a lot of research.
The tax certificates are auctioned off at the sale. The starting bid is 18% and investors bid down from there. You say 'I am willing to accept 17% interest on the back taxes'. Then a guy representing an investor group steps up and says 'I am willing to accept 8% interest'. It is worth it to him because his group is investing hundreds of thousands and he has set up cool programs to track and research all the properties.
It ties up your capital and you really have no idea when you will get it back. Could be three weeks or it could be five years.
All in all, there are easier ways to make money in RE. Like writing books on 'How to make millions buying tax deeds'
