What is the issue with Apple using web tracking cookies?

I would like to know why Apple uses web tracking cookies with web logins.

I have Firefox set to disallow tracking cookies, and I don't go in and hand-edit domains, so I haven't made any particular choices about this domain or that domain. Most websites I use maintain their logins, but Apple and icloud do not: this indicates to me they're using tracking cookies. Why? Can this be stopped?

Because the other annoying thing about it is the required 2FA login every time I visit. My logins are not saved, and I have to do the code with my phone every time. And if I use icloud.com and apple.com, even in the same web session, I have to do the 2FA twice: I can have a tab open to one site, and still I have to reconfirm and relogin on the other, using the same login info.

I feel like this is Apple trying to annoy users into permitting tracking cookies. I'd like them to stop doing that, and make web logins more convenient, while still being secure.