They are not targeting such client base perhaps. They focus on high net worth individuals for their private banking business. While there are hnw clients who own cryptos this share of investments is rather small. Let's not forget that hsbc was not founded 10 years ago but is an institution in business for over 100 years. I personally welcome a conservative approach and preferential treatment for its rather conservative Premier client base (though the premier benefits at hsbc Canada is highly questionable). On the darker side of things, hsbc has been engaged in a lot of questionable investment schemes and money laundering issues so the heightened risk of crypto payment transfers can't really be the issue here
Why wouldn't it be legal? IB bans trading in multiple securities. Gamestop crowd also protested thinking a broker is obligated to offer trading in all securities in a given market.