Even if you ran an Interledger wallet on your phone without acting as a server, you’d still have to be online at all times.
Phones are moving away from allowing background processes so it’s very possible that in a year this won’t work on mobile regardless. And on a laptop it would stop accepting packets once you close the lid.
Better to offer good tools for users to self-host SPSP servers in the cloud than fight the uphill battle of running what is logically a server on a device that isn’t always online.
Personally, I would rather trust someone to host my wallet but I understand why it’s important we offer an alternative to that.
Those are all good examples, and it makes me think that introducing end-users to the concept of payment pointers might be a waste of time in the long run.
All of those flows still benefit from the exchange of an identifier which is not the raw address+secret, though, so SPSP could still have value even if the URL itself isn’t entered by hand. Even in the case where a phone communicates payment details over NFC, it’ll still be hitting a server to fetch payment details unless the phone itself is connected to ILP.