Kitchen Sink Pipes Exposed?

My aunt had all her home pipes replaced, in the kitchen she had new less than a year old pipes but the plumber said they had to be replaced because all the new pipes where PVC (yet he left the old metal shower pipes as is with PVC in certain areas). Now they took out the metal pipes and installed new PVC pipes but instead of running them thru the walls they come up from the floor and are exposed in the cabinet under the sink. Is this normal? legal? at all safe? My worry is that they could easily be broken if something pushes them.