Storage vs brokerage

I’ve been learning about bitcoin and so far it’s still not clear to me why brokerage is not a good place to invest in bitcoin. I had some in Webull as I read that is one of the best places to buy bitcoin. Then they opened Webull pay and moved my funds from Webull to Webull pay. Most if not all of the major houses like TD Schwab etc don’t support crypto at all. What are your thoughts on best way to purchase bitcoin, and why? Thanks