Companies where you have to log in and download invoices are the worst. If there's a viable alternative to their products I switch immediately. You make it seem like it's not a big deal, but a reasonably sized startup has dozens of service providers. Should we pay every little service $4k/mo just to save the communications and context switching overhead?
You jest, but imagine how time consuming it would be if every app we used was setup like CloudFlare, where only the one super admin can deal with billing.
Also in these days of remote work, it's a problem if the credit card details need updating - either you have to give the company card details over a slack call, or you need to give a card holder your root password.