Maths is also one of the easiest A-levels to get an A* in - just by the nature of it. It's very right or wrong, very easy to practice and revise and relatively straight forward for competent mathematicians (i.e. those wanting to do a maths degree). It's a requirement for Maths courses, whereas it's not a required subject for medicine. Medical applicants have it harder with the other hoops they have to jump - it's not about the grades at all.
With a 2.1 in maths you stand a perfectly good chance with decent graduate schemes which can lead to very good positions.