I can think of a reason: an ETF would allow me to save Bitcoin for retirement with tax benefits.
The idea is not good at start. Bitcoin and cryptocurrency give us control on our coins and tokens with private keys
I can (obviously) keep my own private keys, but that doesn't get me the tax benefits. Short version: if you jump through the right hoops to save for your retirement, it's tax deductable. That means you get up to ~50% back from taxes. By the time you retire, your pension income is taxed, but the assumption is you'll pay a lower percentage by then.
The big savings are in the reduced wealth tax: we pay ~2%
each year on investments. If you still have a few decades to go before you retire, you lose about half your money to taxes. You can prevent that if you jump through the right tax hoops.
People who want to use Bitcoin ETFs and other cryptocurrency ETFs will not actually own any coin or token, and if those companies do shady things, those people will gain nothing in their hands eventually. Not only tax but also with a bigger risk, losing all their money to ETFs.
The same applies to any stock market: people are totally used to paying a broker to keep their shares, and the stock market is a lot bigger than Bitcoin. It's a good reason to diversify though, so at least you won't lose everything in case one of them loses everything.