In good conditions, rear brake doesn't do much. In wet, icy, slippery conditions, it is quite easy to cause a front wheel skid which is generally terminal. Recovering from a rear wheel skid is straightforward - some people even do it deliberately, for fun.
Brake cables also snap, especially if they live outside, are old, galvanised, unloved, etc.
In good conditions, rear brake doesn't do much. In wet, icy, slippery conditions, it is quite easy to cause a front wheel skid which is generally terminal. Recovering from a rear wheel skid is straightforward - some people even do it deliberately, for fun.
Brake cables also snap, especially if they live outside, are old, galvanised, unloved, etc.