Parking Charges at TNA

If you park at the UK National Archives be aware that under the innocuous heading "Changes to car parking at The National Archives’ site in Kew" TNA announces they are instituting charges for parking from 3 April 2018.
Why couldn't they be more straightforward and make the headline "Charges for car parking at The National Archives’ site in Kew instituted"?
Most of us don't go to TNA often enough to get worked up about it, but why a tiered charging scheme?
Up to two hours £2.50
Up to four hours £4.50
Over four hours £7.00
If I had a vote I'd opt for, say, a £1.00 per hour basis.

Find the TNA announcement at http://www.nationalarchives.gov.uk/about/news/changes-to-car-parking-at-the-national-archives-site-kew/