Originally Posted by dabac

It's easier to recover from a locked-up rear wheel skid than it is to recover from a front wheel skid, so it's my desire to avoid a faceplant that encourages me to use the rear brake, if conditions are slippery and the available braking distance allows it.

The front brake gets used too, but with more care and a bigger margin against lock-up than the rear during slippery conditions. It's a tradeoff between longer braking distance and a reduced risk of front wheel skid when riding at the limit of my ability. Seems like a good deal when circumstances allows it.