Part of the problem is that the browser just mindlessly goes along with it.
We've got into a situation where the vast majority of users don't know and don't want to know about any of the details of what's going on, and by default most browsers just allow them to be tracked in a variety of different ways. Website writers/maintainers quite often don't know themselves what a framework is doing, and everyone writes using the assumption that cookies are something they can just use. It sometimes looks like everyone except the end user was involved in the development of the situation.
Yes it takes some effort to delete them, but so does looking left and right before crossing the street.