The purpose of top-up fees gets attached by universities and government to the purpose of education. To an education professional the purpose of education is often to impart information and skills in a framework that is completely owned by the professionals themselves. To a “consumer” of education this looks less obvious. How can a consumer know that what they are getting is worth a top-up contribution?
My take on the purpose of this political move is that it is a set-up not a top-up. By raising the question with would be students as to whether what they are “buying” is worth even the top-up, let alone the full amount, the government is trying to unleash consumer power on the universities, who it would like more control over.
This situation is already out of control. Universities conduct completely spurious back-filling exercises to show that they “planned” their research programmes to give the outcomes that actually occurred as part of generating favourable research assessments necessary to attract students. You can go a long way to find any solid foundation for any of the ostensible purposes in this smoke-and-mirrors set of systems.