James Farrar wrote:

There have been movements to create an alternative to NUS. NUS tends
to be unpopular because of a perceived closeness to the Labour Party
(backing tuition fees in 1997 really damaged its reputation) and that
it seems to care more about furthering the individual political
careers than about helping the students it is supposed to represent.

That's a part of it, but I think a bigger gripe stems from the high fees and
a strong sense that it isn't good value for money or terribly responsive to
what SUs want. For example the last NUS Conference in March did not even
debate the university lecturers' marking boycott, with the result that the
NUS position was decided by the National Executive and many SUs went public
in their opposition.