It is NOT a bad idea. It IS a good idea. Installing the oil catch can will prevent oil build up, caused by "blow-by" in the intake. The concept is pretty simple. The contaminated oil is stored safely in the catch. When you doing an oil/filter change, you dispose of the contaminated oil stored in the catch can.
The PCV system draws a fine oil mist that gets included to the A/F intake charge. This can lead to reduced combustion, a dirty throttle body/intake manifold, fouled spark plugs, and more.