I don't know how it is relevant what Apple did on other products, especially "pre-iPhone". The point is that TODAY the PC line and the iPad line of Apple are q

I don't know how it is relevant what Apple did on other products, especially "pre-iPhone". The point is that TODAY the PC line and the iPad line of Apple are quite notable silo'ed to very specific usage-patterns. There is no technical reason for that, but the distinct commercial reason that there is nothing to gain in terms of revenue or profit by combining the two products into one. They both sell fine and at great margin separately, there is little to gain by building an iPad Pro that is 2000 USD and supports the use-cases of both a 600 USD iPad and a 1600 USD MacBook respectively. Quite bluntly: You want the iPad to be convenient in a workflow as far as possible, and then SUCK really bad in a way only a fully synchronized Macbook can fix.