The designers of the NTSC system knew theoretically that it would be possible to properly separate Y and C, but did not have a cost-effective way to do it in the early years. In fact, the more sophisticated methods of separation through "comb filters" did not arrive in the market until the late 70's, more than 20 years after the system was adopted.

So, early television receivers used the notch/bandpass filter system for Y/C separation because the method is low cost and easily implemented with reasonable results. In many situations, that approach is used today. In fact, most all of the digital decoders on the market automatically switch back-and-forth between notch/bandpass and combing as required. Watching a VHS tape? You'll most likely be operating in the notch/bandpass mode even if you have a comb filter in your display. Why is it called a notch/bandpass filter?