[insane_dreamer]

I never carry cash with me.

I almost always pay with my phone using tap.

Some restaurants have a fully online payment system where you get the bill on your phone and pay from there through some online payment system. I've seen this at airport restaurants, where it makes sense as you may be in a hurry and don't want to have to wait to get the server's attention. I wouldn't like it at normal sit-down restaurants in other situations.

I don't think this is a technology problem. There are lots of lo-tech ways of signaling that would like the cheque.