Sure you can indeed. For me the compactness of the rpi was a plus however. Since you don't need a dedicated screen or a keyboard (recalbox interface is tailored for controllers), having only to carry the small rpi makes it more convenient and more suited to this use in my view.
Of course, if it's to play at mainly at home then I agree it's not as interesting.
I can bring two old corded Xbox 360 controllers with my Surface Book 3 and play pretty much any console game on an emulator. My SB3 has an HDMI dongle that I got with my SB2, so I just struggle to see the point.
I bought an SNES Classic, and it sits in the box because I can emulate all those games, plus more, with better graphical quality and more features on SNES9x.
Of course, if it's to play at mainly at home then I agree it's not as interesting.