hmmmm.... it has anything to do, one thing with the other.
There are cassette recorders that use the 2 tracks per side and make it 4 tracks only one way (keeping the width of each track) and there are 8 track cassette recorders that divide each track into two (reducing the width of each track) but that depends on how the machine was thinked about and built.
If you have a 8 track recorder, you have an 8 track recorder, period. Doing what you are doing (recording the same thing in two tracks) is just nonsense.
To get wider tracks you would have to get an analog recorded that uses 8 track tapes as a 4 track recorder to have higher fidelity, that I really doubt anything like that exists.
Instead developers think about the most optimal combination of elemts to get the best sound overall (x inches per track, noise reduction, tape speed... etc)
You can double your voices and guitar and stuff, but that is more an artistical issue to give more power to the voices for the chorus for example, but has nothing to do at all with audio fidelity.
Hope I was helpful
