Yeah - I don’t think the user base interested in container UX is “large” in relation to the mobile world.
Also, who wants to carry around a display with its own battery, a keyboard with its own batteries, a mouse/trackpad (batteries) and cables for the above? At some point it’s honestly easier to just grab a MacBook Air and walk out the door.
And I don't know, the container UX people didn't exist for ChromeOS before ChromeOS made it easy to run Linux apps that way so.