The subpixels are entirely hidden on any display that isn't complete garbage. I just had a look at my phone screen through a good zoom microscope and I needed at least 8x magnification before I could start seeing hints of RGB color. At the same level of magnification, I can easily see individual grains of toner and strands of wood fiber on a printed page.
The "existing convention" is a legacy from the days when 72ppi was accepted as the "standard" display resolution. Anything with an acceptably high-resolution display can do whatever it likes with the subpixel arrangement and it won't make a bit of difference.