> [AI agents ] ordering transport, booking restaurants, managing email, conducting research, writing messages.

My single most used app is my web browser but let's look at actual apps. Those examples might be just random stuff, but how many restaurants and transports one books per day? I guess that most of the activity is passive consumption of content. You need an app for that, they won't let their competitor agent scrape their content.

And finally, if instead of messaging my friends I'm chatting with their butlers (the agents,) and they are chatting with mine, why should I message my friends anyway?

"Ok Dave, I'll look that up right away but in the meantime, have you considered switching your insurance to Best Insurance Company? ..."

Basically --- non visual ads that can't be blocked --- the delivery mechanism is an inherent part of the AI operating system.