the way I see it is if a rod is made for a maximum of 14lbs it's not going to be able to lift 30lbs so why put 30lbs line on it? just use a heavier rod
Because using heavier line significantly reduce your chance of a line break. This helps a lot especially with snags (as long as you pull it the right way, either with your hands or something other than the rod).
Also, just because your are putting on 30lb line doesnt mean you have to lift 30lb.
People land 20lb fish on 8lb line.
Again, just set the drag right. If Im using a 50 lb line on a rod thats rated 2-8 lb, and I set my drag to 5 lb, I can only put 5 lb of lifting force on the rod before the drag gives in. No chance of rod breaking. Of course im not telling anyone to do this, but just as an example.
Going over the line weight limit wont change anything imo, as long as you dont mind the less sensitivity/line capacity from the line.
My pike rod is rated at max 17 lb, and I use 25 lb line on it no problem.