While it's true the front brake is responsible for a hugely disproportionate amount of the stopping power, this is only applicable in ideal riding conditions - both
brakes used in unison & varying amounts of pressure (depending on conditions) is the proper way to brake... that is ofc why there's two brakes and each with independent control. As a year-round rider, this is a lesson I've learned well.
When it's nice out and the pavement is clean and dry - sure, I only use the front brake (mostly jus' sheer laziness)... but if I'm dangerously close to a lockup and/or there's even a little sand you better believe that rear brake comes into play. Adding stability, even if the braking power of the rear is a mere 10-20 percent - that's more than what you'd have by not using it. Assuming a panic stop, should the front start to get squirrely it's nice to already be crankin' down the rear when you lighten up the front.
I'm a devout proponent of front brake use - but don't get the idea that the rear one has no "influence" at all, the only
time that would be true is if the rear wheel actually did come off the ground and if that's the case - it'd hafta be almost perfect conditions & improper weight placement... a fairly unusual occurrence unless done on purpose.
Best bet? Practice using both
while remembering the front gives you the stop & the rear gives ya stability