The main reason why Curve has not expanded to BNBChain after all this time is because BNBChain tokens are pegged by Binance. This means that BNBChain tokens are backed by Binance's own cryptocurrency, BNB, and are used to facilitate trading on the Binance Chain. As a result, Curve has not been able to find a suitable way to integrate its services with BNBChain. Additionally, Ellipsis is available on the Binance Smart Chain network, which is a more suitable platform for Curve's services. Therefore, it is likely that Curve will continue to focus its efforts on the Binance Smart Chain network instead of BNBChain.