You can see those things with just server logs.

No, you can't. There's no way to get viewport from server logs, and presenting them a form digestible by marketing people isn't easy.

And for all of that, you need GA because...?

Because it's easy and marketing people can work with it. Access logs don't have all the information ( e.g. viewport) and are cumbersome to parse.

I get the gist, you believe you’re so bad at running a shop and/or writing you can’t survive without creeping on people.

Also, look at both of your examples. They’re bad. They’re both best replied to with that diagram of holes on a WW2 airplane.

If you're trying to buy from me, who you are is literally my business.

What I buy from you is your business. The information I give you to complete my transaction is your business.

Who I am is not.

You don't need to know if I have kids, have a disease, my age, my race, my gender. You don't need to know anything. Sure that information would help you make a better experience for me, I get that. But that's up to me. If I want a better experience, allow me to provide that information in exchange for the benefits that information gains me. But peeking over my shoulder as I walk through your store so that you can overanalyze everything I do isn't okay.

And I'll happily fill out a form to tell you any information I feel is relevant to my purchase. If you want to covertly fingerprint and track me, I'll gladly take my business elsewhere.

No it's not. My shipping and payment details might be, if I decide to buy anything. Those are not the same as "who I am."