It doesn't surprise me that CashApp has been this popular, especially with how Coinbase, which is usually the main newbie fiat onramp, is annoying people with their insane fees.
People now have an alternative option that's cheaper (cheaper means more BTC for your money). Not only that, it also offers an alternative to PayPal with how it has been annoying users with account blocks and other nonsense.
The benefit there is that even people who aren't into Bitcoin can accept it for their goods and services and from there cash out if they so wish. Jack Dorsey definitely has his priorities in order.
As for the weekly limit CashApp subjects users to, I don't think it's a problem with how most people don't have $10k to blow on Bitcoin. Those who do want to buy more go to an actual spot exchange to buy in big.