Whilst you maybe right technically, on £100k* a year you take home £66k after HMG has taken their total deductions and that's before pension contributions.
Rewarding people who do the education, work their way through the lower paid roles (servicedesk -> admin -> consultant -> architect etc), do extensive training both paid and in their own time and obtain related certifications is perfectly reasonable in my view.
I don't agree that taking 44% off their renumeration is reasonable however. When I was getting paid for servicedesk or IT admin roles I was losing 21% of my renumeration. I kind of thought the point of percentages was that it scales by it's nature...
Whilst I'm sure some people may think I'm being ungrateful or pompous, on my generous (but hard earned) salary, should my employer offer me a one off £1k bonus for passing a rigorous or particularly tricky exam that may take me weeks of study in my personal time I just wouldn't really bother now. When I was earning in the 20% bracket then I did. Mainly because as a 40%'er my time is more valuable yet I'd be earning less per hour for the studying effort than when my time was less valuable when I was more junior.
50 hours of study to take home £800 (20% rate) is £16 an hour.
50 hours of study to take home £600 (40% rate) is £12 an hour.
And of course you're more likely to be paying 40% if you are older and thus have a family to spend time with or have wealth to spend on holidays and probably more advanced in your career so career development is likely to be less essential. Arguably this could make your free time as a 40%'er more valuable, and thus earning even less per hour than a junior fresh out of collage even more perverse.
*I do appreciate that £100k is a great deal of money. But I think it's reasonable for people who did well in their education, have done extensive training, work very hard in technically demanding roles and worked their way up the career ladder to be paid a good chunk more than someone in a less skilled or challenging role.
Let's say an office manager is paid around £33k who does valuable work but is internal, non-technical and not particularly highly skilled. Then I don't object to a cloud architect being paid 3 times that to be honest (I'm biased of course) - mainly as the higher paid role is customer facing, has extensive deliverables they are solely responsible for, requires extensive and regular training, is highly technical and is ultimately a specialist role.
The office manager loses out on 21% of their renumeration vs. 44% for the cloud architect. That doesn't seem that reasonable to me given the work required to become a cloud architect and maintain that role, particularly when the pay gap is tens of thousands, not hundreds.