[naet]

Big companies hire "digital marketers" who try to push metrics up to justify their jobs and salaries and demonstrate some form of growth.

Why do you see intrusive cookie banners on every website? So they can force people to hit accept and get their GA metrics higher. Why do you see login required on many pages? So they can get their login / registration numbers higher. Companies might lose some anonymous viewer traffic when requiring a login, but the money is largely made off of targeted advertisements for logged in users so they want to push you in that direction and harvest that data.

You might be deterred into not using a service by that popup, but the data shows that enough people will just go ahead and sign in or register and so it's worth it to the company to add it. One of the first companies I work for had me add a big modal that asked you to sign up for their newsletter when you visited their homepage after you scrolled down for a second. I thought it was intrusive, but it absolutely got people to sign up so I couldn't really argue with it.