Just because it hasn't happened yet is not a reason not to do something. A tornado hasn't wiped out my house yet, should I move because it might happen some day? Of course there is a risk associated with their use, but the estimated risk is miniscule. It's not even measurable yet. Let's worry about problems we can identify and solve rather than wasting time fretting about what may be.
If by "risk" you meant the horizontal transfer of resistance, then I point you at genomic studies of horizontal gene transfer across bacteria. It happens with such regularity that the concept of a species cannot be naively applied to bacteria.
