Most projects are still turning into an ERC-20 token, because the Ethereum blockchain is decentralized. This is more important than speed/low costs as it guarantees censorship resistance. It's no wonder why Ethereum is still a popular choice among everyday people. Aside from the fact that BNB is fairly new to the crypto/Blockchain space, it's model is utterly centralized. Binance has large dominance over BNB's blockchain network, greatly increasing the risk of a single point of failure. It's BNB's level of centralization which has lead it to enjoy blazing-fast transaction speeds and ridiculously low fees. Depending on a person's preferences or needs, will be the type of cryptocurrency to use for daily payments.

All in all, it's evident that Ethereum is the most trusted altcoin in the world. BNB will still have some supporters behind it. But ETH will remain as "king" of the smart contract industry. The more projects build on Ethereum, the better it'll be for its adoption in the mainstream world. The Binance Smart Chain (powered by BNB) is going to have to adopt Ethereum's "EVM" in order to become compatible with ETH's smart contracts. Only then, BNB will be able to enjoy mainstream adoption like ETH. Otherwise, not many people will use it. Just my opinion