I will answer this question based on the environment where I live.

Yes, I've heard of the technique of burying money underground, especially from films, but I've never heard of real people around me using it to protect their money.

I don't think it's viable anymore, especially for money, because it's not flexible and has many drawbacks, like no interest earned and the value of money depreciating due to inflation. Unless stored correctly, the money might deteriorate and become worthless.

Perhaps for gold, silver, or jewelry, it's still viable as long as it's sealed properly and buried for the long term, as their value tends to be safe from inflation.

But as for myself, I wouldn't do this because I live in a densely populated city, and there's no place to bury it safely without other people knowing. Besides that, I still trust banks, and the flexibility of using my wealth is important to me.