Having not used Public Transport for well over 10 years,I pre-booked a rail ticket .
Manchester to Farnborough, The bus to Manchester was £4, they accepted cash ~7.30 AM. I would NOT have contemplated buying a prepaid card with a balance I am unlikely to use for another 10 years (1996 and 2003 were my previous PT journeys, all for ferrying a vehicle for someone else)..and before that,1978, when I returned the Company Car and became Self-Employed.
Public transport works in London. My non-driving son is quite happy to live there....Daughter who lived in Woking,still had to keep a car....frequency,convenience and cost precluded sole reliance on PT.
As a London Visitor,on a one-off,Lifetime holiday,I'd probably succumb. buy a card and give away the credit when I departed....otherwise, just another good reason to avoid the Mighty Metrolopis.
This sounds a similar "stitch-up" to Direct debit energy-bills (ALWAYS overcharged, you have to fight to reduce thepayments to a realistic ,near zero annual balance)
Irresponsible, arrogant and concieted self-serving beaurocrats.
but, bugger the visitors, they only come once!..(Well,they will now!)