But as for wallets in smartphones, we can use them as well if the shops and merchants accepts them directly.
I think Stellar is supposed to be able to do this as a built-in feature, though I am not sure offhand whether specific smartphone wallets such a for example LOBSTR have or have not provided access to that feature.
In theory you are supposed to be able to tell Stellar what asset the recipient wants to receive how much of and it shows you for each asset you have how many it would take to have that happen, so you can pick from your portfolio which you want to use to make the recipient receive what they want.
-MarkM-