How would it be less fair to permanently imprison a repeat DUI offender than it would be to wait until he's actually killed someone before locking him up for go

How would it be less fair to permanently imprison a repeat DUI offender than it would be to wait until he's actually killed someone before locking him up for good. Perhaps I'm misguided, but it seems to me that its more fair to impact the life of the offender than it would be to allow an innocent person to die. Fortunately, there are more than two options. The best idea I can come up with would be to permanently suspend driving privileges for anyone with a second DUI conviction.