It's even worse than this, because they don't even have gold (or bitcoins in this case), what they have is an IOU for bitcoins on a bank account (at Binance): this is fiat bitcoin and it has even lower guarantee than fiat dollar, since Binance is far more regulated than a regular bank.
I can at least easily/cheaply convert and withdraw it as one of many cryptocurrencies. Of course, if Binance went away or otherwise restricted withdrawals, then I wouldn't have access to it, but that's the price you pay for the convenience and features of a centralized exchange.
Some of the newfangled DeFi cryptocurrencies try to get around this, but of course they can't offer a visa card.
As with all things, its a trade-off. For me, Binance is a better trade-off than my bank, for the things I use Binance for. I also don't exclusively use Binance and I do keep some of my crypto in my own wallets, separately from the centralized exchanges.
