I use it because I view the dollar as a debt based slave system I'd prefer was replace with censureship resistant sound money. BTC is pretty okay at that, but my preference is currently Monero.
Most of crypto is used in Decentralized Finance, basically an open source version of the activities done on Wall Street. Very little is used for everyday goods (and you're right, why bother when credit cards give much better rewards)
Have you bought options with your credit card? Borrowed money against collateral? Purchased and collected revenue rights to music? Traded oil futures?
These are the kinds of things I'm doing frequently on Ethereum.
All of those things have better protection in traditional finance. Sure, they don't have credit card consumer protection, but they do have other protections.
Unless you're using blockchain financial instruments in order to do more blockchain stuff (the circular use case), the other options are better.
Trading oil futures doesn't need cryptocurrencies. And if you use it anyway then you expose yourself to additional risk not in traditional finance.
E.g. the difference between FTX shenanigans hurting investors (who are now being victim blamed for "not your keys, not your coin") and anyone financially reliant on Tether shenanigans (which includes all holders of BTC) is that Tether seems to be getting away with it, by so far not being subject to a liquidity check / bank run.
You can still always fall back to the government if disagreements occur. The advantage of smart contracts is they automate away the need for costly lawyers in the good case (which is most of the time). You don't need to pay so much overhead for "protection".
The benefit an open finance platform provides is you don't have to have some blessed middleman that conducts the trades or holds money. There are a LOT of these middlemen in finance and many of them are rent seekers abusing laws to their advantage, and working to add more laws to entrench their company as "part of the system".
Then there is the problem of bigger players using their power to "change the terms of the deal" and force smaller players to comply or spend years in court challenging them. When the terms are coded ahead of time and the platform is neutral there is no entity they can corrupt to get their way and the contract executes as specified.
Lastly these systems are transparent, anyone can monitor and report on companies doing dodgy things, rather than a few overworked government bureaucrats. It also makes everything composable with everything else, anyone can build their own Bloomberg terminal equivalent, which is amazing.
FTX isn't DeFi BTW, they were an unregulated opaque trading firm. They are exactly what is wrong with finance.