I think that's more of a technicality of billing you for a service than something by design

("the tap on - tap off Oyster/Presto card " => Google sent me to "List of public transport smart cards" so I assume you're refering to some branded public transit system)

No, it's not a side-effect, it's a deliberate decision. You used to be able to get an Oyster card anonymously and top it up with cash. I still have one, but they are not accepted now.

You can buy Oyster cards at many newsagents, and top them up there too. There will probably be CCTV, but privately owned by the shop.

Thank you. It seems like I was misinformed. Last time I was in London my old Oyster card wouldn't work and I was told I couldn't top it up (which is probably true) and I couldn't get a new card without ID (which seems to be false).

Apparently even the first generation Oyster cards should work [1] so at some point I was also misinformed.

On Trip Advisor some people say cards can become deactivated if not used for years, but staff in a ticket office can reactivate them.

[1] https://tfl.gov.uk/fares/how-to-pay-and-where-to-buy-tickets...

Presto is Toronto’s equivalent to London’s oyster card.

Actually there’s no tap off IIRC (unlike the Dutch chipkaarts) but still, I would assume the modern station where you enter is a veritable panopticon of CCTV, RF signal interception, etc

Used to be possible to buy and top up oyster with cash. Don't know if that's still the case and you will still be on CCTV at every station anyway.