I understand your question, so let me try to answer from the perspective of a person that has flirted with using the iPad as my primary device. For 80% of what I do, the iPad works great as a tablet. The touch interface is fine, and I can do a lot of light productivity tasks without a keyboard and mouse. Things like: create short draft documents, responding to emails, taking notes, annotating PDFs, etc.. But, occasionally, I have some heavier lifting to do, such as: Lengthy documents, complex spreadsheets, etc.. When these occasions arise, a keyboard and mouse would allow me to get the other 20% done on my iPad. So, I don’t need to own both a Mac and an iPad. Instead, I have a light portable and relatively inexpensive (I am thinking $500 iPad Air 3) device for most of my computing, and a keyboard and mouse back at my office in the house for the more complex stuff.
I know I know that this will not work for everyone. There are people that need a keyboard and mouse all of the time, and they should get a laptop. I am just not one of those people.