I kinda do that with Samsung DeX. You plug it into a USB-C dock and it basically turns the phone into a computer. With Android apps running in little windows (not MS windows). It's amazingly useful, it's a bit like Microsoft's old convergence idea but it actually works.
I use it at work when I forgot to put my laptop in my bag (at home it's hidden in a dock behind my screen so it happens from time to time). I can work a whole day with meetings, doing some MS Office work etc. And if I need real Windows I can connect to a VDI. I could technically work like that every time I go to the office, the only reason I don't is some AD admin work that is not allowed in a VDI. It works technically but it's an internal rule thing.
I also use it on the go with an Xreal Air and a foldable keyboard. I have a whole computer with me for the weight and bulk of less than an iPad <3 It's awesome.
Apple could easily do similar, however their do really thrive by selling as many devices as possible so I doubt they would do it.