Obvious answer is, the Government is a Tory Government so it goes against all their principles.
But why not tax the super rich another 5p in the pound? And the medium rich another 2 or 3p?
Or how about asking people who are supremely wealthy and have masses in savings and property and pensions and trust funds for their children volunteer to live on £2000 a month for a year and donate the rest of it into a pot?
Really ... why not?