MIDI was awesome for its time and perfectly suited for the 8-bit microprocessors of the era (Z80, 6809, 6502, you name it). Now we're in 2020 and the interfaces and electronics have evolved !
OK, Open Sound Control uses 32 bits but I'm not wanting to waste bandwidth for the sake of it. The motivation is mostly because I want to use SPDIF which uses pairs of 16 bits values and reasonably fast ADC easily handle 16-bit samples (hey, that's CD quality !) and beyond this resolution, it's more noise than anything. And the https://www.wiznet.io/product-item/w5300/ has a convenient high-speed bus with 16 bits.
Of course, if only 8 bits make sense for something, that's fine and bytes will be packed.