While I agree with you, a simple process for tourists to use WeChat Pay/Alipay shouldn't cost that much money to create. I really guess at this point they simply don't care.

In Singapore, for example, they allow tourists to use their Visa/MC to use public transport just as locals can use theirs, but add 50 Singapore Cents (2 RMB) per DAY, so for shorter visits, it's perfectly convenient for tourists.

For China, I'm fairly sure they could slap together a device in a matter of hours that could be setup at all airports with international flights.

Function: Charge a foreign credit card with 200 / 500 / 1000 RMB, and add the funds into WeChat Pay / Alipay (So local merchants would get the same fees charged as for local accounts) - make it that WeChat Pay/Alipay only works for 30 days for this kind of prepaid function, and will auto-refund whatever funds back to the credit card it was paid for. Slap some 3% fee on it (for the refund only) so people will try to actively use their wallets more..

Pretty sure such simple device/process wouldn't cost much to implement, and actually make quite some money on fees/FX rate conversations.

The ONE thing I can see is why they don't want such a device is this would allow tourists to buy food/drinks/goods easier at local shops, rather than overpriced "tourist" places.