When the congestion charge was first introduced it made a limited amount of sense. The subsequent expansion was a money grabbing excercise.
Cars are a captive audience and so easy to get more money from.
The options for the government are these.
1) Make public transport so reliable and cheap that nobody but a fool would use a car. It can be done, Friends living in Madrid would no more drive to work than ski in. This costs the authorities money.
2) Make cars so expensive that it's easier to allow an extra hour, ninety minutes, to get into work and although the system is dirty, unreliable and costly, it's still cheaper financially. It just costs the punter an extra five to ten hours of their own time each week. Cost to authorities zero, with the added benefit of extra cash coming in from people forced to use private means. Shift workers, like hospitality, cleaners and, oh yes, nurses.
Motorcycles are for winners. No congestion charge, no ULEZ charges.
Mr Khan's dad was a bus driver you know.