Yes, it can be. The reason it's built in to the mic is to protect the mic's output transformer from distorting when recording louder sounds. Most newer/cheaper designs of condenser mic use solid state outputs (unless they're deliberately apeing a classic design) which typically are less easily saturated by loud bass sounds.

I'd guess NPR's view is along the lines that, well, the filter's already there, and we like the way it sounds, so we keep using it.

It could, but the results might not be what you expect.

Maybe you want to preserve the bass of interstitial music or program audio jingles or environmental effects or something. Doing the processing after the mixing means it affects the whole mix. Doing it at the input means you can tailor each element.

Worse, because bass has an outsize effect on the total energy in an audio signal, if there's any sort of dynamic range compression while the bass is still included, the presence of the bass triggers that compression to happen. Later on when the bass is removed, the remaining audio has inexplicable fluctuations in its volume, which can sound super uncomfortable.

This "program level bouncing around in response to a signal which is not part of the program audio" effect can also come from side-chain compression, and arguably filtering after compressing may be a form thereof. Once in a while it's done to great artistic effect in music, but in talk settings it's almost always horrible and disorienting.

I had just made a comment about how, yes, the studio engineer could do a high pass at the console during a live session but then I had a thought. Perhaps they train everyone to use the HP switch so when they are doing recordings without an engineer that they still get the same sound...? IDK... To me it sounded more like a "policy" than a true part of their "sound". In other words... it's a training function that makes the engineer's job a little bit easier.