Not every computer is of equal value for the multiple things you need to do: Taking notes is easier on an iPad. You can’t take your iMac on holiday (well, you could but it wouldn’t be very convenient). Android sucks for gaming. Reading isn’t much fun on a laptop and so on.
The iPad Pro (not an iPad most people should ever buy) is the closest I’ve come to a Swiss Army knife computer. There aren’t many things it’s bad at and even if you want PC-quality games you can stream them from the cloud or direct from a console.
But even with an iPad Pro as my road machine I still keep a Mac Mini at home because there are still high-end tasks I need a desktop for.