If, day-to-day, you only use the front brake, then when you need to stop suddenly, you'll be experienced with using the front brake.

The problem is someone who uses the rear brake 99% of the time, then grabs the front brake when someone steps in front of them...

Breaking at similar speed on the rear brakes will cause a fishtail and slide rather than brake. I'd rather endo (flip over my handlebars) than ride in front of a car.

Never had that happen to me in over 35 years of riding bikes. I do go over the handlebars occasionally. I have had the front wheel slide from under me a few times as well (my least favorite way of falling). I even ride with a low tread back tyre so I can slide the back wheel around a bit on trails.

Maybe you instinctively apply appropriate pressure using the front brake.

If you slam on the rear brake only or simply much harder than the front brake, the rear wheel locks up before coming to a stop. The bike will continue forward with the front wheel rolling and the rear wheel sliding. If there's slight braking on the front wheel, the rear starts sliding around the front, twisting the cyclist.

Fishtails are pretty easy to control though. Going over the handlebars, not so much. (though that requires a lot more braking power, to be fair)