Exchanges need promotion like you have said because they need new customers. Banks have been in existence for a long time now and they don't need such kind of marketing or promotion as they know customers need banking services to survive in this world. Crypto has been in existence for a decade and as it is a new concept these exchanges need to lure new customers in a competitive crypto exchange market.
In reality, Banks are safer to save your money than exchanges, because Banks are regulated by central banks, but an exchange can go bankrupt or be hacked at anytime and investors funds will be gone. Despite the advantages of leaving my coins in exchanges, I'll rather leave them in a none custodial wallet, where I'm the custodian of my coins.