What makes the front wheel brake a bad idea? I almost exclusively use the front brake, because that's the one that'll actually stop me. (Source: when I used rim brakes I had to replace the front brake pad three times for every time I replaced the rear brake pad.)

I know some people use the rear wheel locking up as a way to sense when they have applied enough front brake, but that's not necessary. It's also possible to learn to sense that directly.