It may not make financial sense for someone retired, not into tech, and/or data privacy to host their own LLMs. However if usage of AI in day to day lives continues to increase, I think it will eventually make sense for the majority.
Many tasks suited for AI assistants are background asynchronous tasks. They can run in the downtime where immediate demand is low, keeping overall utilization high enough.
Your argument is similar to those who argue that owning a GPU for gaming doesn't make sense when you can stream from something like GeForce Now. However like with gaming locally (improved latency) there are also benefits to local AI (data privacy).
Another big benefit of local AI is control and increased predictability, e.g. in costs or behavior.
We will appreciate it even more when popular agents become more costly or start including more ads.