You are right, BNB is always supported by Binance as the largest exchange that always has a way to maintain and support BNB. While polkadot does not have a strategy like binance, but I am sure that over time the DOT team will also have an exchange, we will see in the future.
I'm not sure about the Web3 Foundation introducing its own CEX to support DOT token. Building a CEX isn't the job of a blockchain project, instead, a CEX can build its own blockchain based on existing technologies. For example, Binance has BNB chain, OKX has OKchain, Huobi has Hecochain, and Coinbase has Base.
It's true that DOT doesn't have much real-world value for users yet. The main driver behind DOT price increase during the bullrun 2021 was parachain auctions, but this is no longer relevant now. I can only hope that the demand for cross-chain and Web3 apps will increase in the coming months to boost the use of DOT, creating buying pressure in the market and triggering a price increase for DOT, making it as attractive to investors as BNB has been.