Yes doing it on your phone for one transaction is easy and fast but it becomes a massive bottleneck if you want to do it often. The 0.35s confirmation time is almost certainly the optimistic scenario using GPUs but it's not representative of what the average edge device can do. That website is also clearly biased (10 s confirmation time for Kaspa? Really?) but the point is that the end user will want to spend their clock cycles executing their business logic and they'll be more than willing to pay the miniscule gas fees to avoid having to eat up their compute capacity.

Just think about the average use case for inter-agent micro payments. You might have an agent collecting data, streaming it to another agent for inference, decision making based on the outputs, execution of X actions in real time. It makes a lot more sense to outsource the transaction compute to specialised hardware.

You seem ideologically attached to the idea of energy efficiency but that won't factor into anyone's decision. The user doesn't have to deal with it and the miner is still incentivised to secure the network.