Hi there,
Allowing the taskbar on the side is a big advantage and therefore Microsoft should have this made available. Besides that it is more convenient for some, it also comes with the practical benefit of showing more open windows that I can select from before they get stacked.
Usually softwares get smarter and offer more options, not less. I don't understand why Microsoft wants to decide on my behalf what is better for me. It should be as customizable as possible because people work differently and it should be all about efficiency for the users who pay for the software.