Oyster wallets - being seen

Thinking again about the various factors that make these such a popular promotional gift, it struck me that they are one of the few gifts (umbrellas are another?) where other people will, on a daily basis, see the wallet as - at so many different public transport places - they are pulled out of pockets and bags, 'flashed' and put back again.

Even without realising it, other people will see the logo, the colours, the message etc.