This is not always the case and is a decision to be made by the engineer based on two things. The first of these is if the pop screen has a negative effect on the sound. I have repeatedly noticed that standard nylon pop filters can muffle recorded sounds, and can make a sound mimic comb-filtering or other unwanted noise. For sound quality you would not record an Amati violin through a double layer of their grandma’s tights, so why do people do this automatically with the most important element of their tracks, vocals?
The second is that, most of the time, a pop filter isn’t even the best solution to the problem it’s intended to solve. Problems with speech pops and distortion usually suggest either poor mic technique on behalf of the singer, or inappropriate mic placement on behalf of the engineer, or both. In a lot of the sessions I've witnessed trying to teach an artist the proper way to sing/rap in to a mic can lead to egos flying and a varying degree of success. So use discression because none of us wants to expose our precious microphone diaphragms to a volley of spit!