If Binance were renowned for supporting/promoting Bitcoin, you can then prolly ask this question as to why they are yet to see the need to integrate Bitcoin LN, but Binance do not support Bitcoin as quite a lot of people erroneously believe, Binance prioritizes profit, and profit alone. They prolly look at Bitcoin being decentralized and imagine that they can't really gain anything promoting it, thus they would choose their shitcoins over it everyday, they can play around with them for profit, something they can't do with Bitcoin.