These kinds of consent forms are often designed by advertising companies using the IAB consent framework. The idea is that once a user has opted in on one site,

These kinds of consent forms are often designed by advertising companies using the IAB consent framework. The idea is that once a user has opted in on one site, their consent will carry over to every other site using the same framework. Naturally it's in their best interests not to allow you to mass opt out. This kind of behavior may be going against the spirit of the GDPR, which states consent must be "freely given". Presenting hundreds of check boxes to click may be considered coercing the user into consenting. Will be interesting to see the first rulings about these kinds of popups and the even riskier "consent-walls".