Ipads have had proprietary Apple keyboards since the 30pin connector. I have one for a gen1 ipad in my own collection and while they didnt ever release an ipad specific mouse, their BT enabled wireless magic mice can connect to ipads, so I do look at them as a viable desktop experience if one wanted them to be. I know my mom n dad for example (73 and 81) use their ipads for probably 90% of what they do on the internet day to day despite having dedicated imac desktop and MBPs.
I think alot of people use their Iphones as their primary interface to the internet. Short of writing a 30 page essay on one or working building dense databases, they really can do most of what folks consider daily driver tasks ie: email, YT, video chat, text, purchases, music listening and creation, light games etc. as well as multimedia like video & photo creation and manipulation and they do it really well at this point. I am an avid digital photographer with many DLSRs yet I love using my iphone14 for in the moment photography. The cameras have gotten amazing my Wifes iphone16 pro max camera is jaw droppingly fantastic and fun to use.
My prefernce for heavy work is still a desktop with fullsize kb but that is becuase I can type and was in school when kids still learned typing in typing class on an actual typewriter lol. Jeez, even voice dictation which stunk for a very long time is getting quite good where folks wont ever have to touch a kb or learn to type - just dictate their thoughts and the i-device picks it up and drops it into a text file. I absolutely see iphones and ipads replacing desktop and laptops for many peoples DD tasks as well as pay-the-bills job work as the technology matures and continues to advance. Really I think it already has done this for many people.
TLDR; lol Yes I see more people spending large amounts of time on their portable iphone/ipad devices.