That and: If you're already ingesting your financial data into something like Quicken, Banktivity, MoneyDance, etc. you're rarely going to be hitting the issuer's website, other than to make payments (and maybe not even that, if you have auto-pay setup). Between investment accounts, property loans/mortgage, cards, my business accounts, etc. I would go nuts if I had to bounce around to different websites all the time to gather financial data. In a situation like that, Apple Card's "oh we have our special little app you can only use on your iPhone" is a liability, not a benefit. But that's me, others may not have as diverse a financial profile, or be as comfortable with their own system or process like you are. For those, sure, having it be yet-another-app could be a benefit. I just don't see that it's so strong of a benefit to overcome what a lackluster overall card it is.
Apple Card has always felt like a really good idea that, like so many good ideas at Apple, started out with promise and now is being left to wilt. They need to be much more aggressive about developing it as a product. Personal credit is hugely competitive and I'm not going to sign up just "because Apple."