Microphones need tremendous amplification to even get them to "line level" signals to interface with other audio equipment - 60db is not uncommon. Bass signals require a great deal more power (watts, or in this case milliwatts) to amplify accurately than midrange/treble signals, so they're a lot more likely to cause distortion. Rolling bass off as early as possible - preferably at the capsule, before the microphone's internal circuitry - reduces distortion.
Beyond that, with a few exceptions, most of the signal rolled off by the switch is stuff you don't want to hear anyways - "plosive" pops, rumble from low-frequency buildup in rooms, vibration, etc. Much of it can't even be reproduced by most speakers (speakers don't do low bass because, as said before, it's a hard problem and not actually audible in most cases).
As an aside, when mixing records, I'll often roll off guitars at 200 or 300hz, losing a couple of octaves of low-frequency information. In theory, this is awful. And if you listen to the solo guitar tracks, it's awful. But in an actual mix, it's great! It gets the low end of the guitars out of the way of real low-frequency instruments like bass and kick drums, making the bass sound tighter and cleaner. The guitars sound clearer too, because they aren't getting muddied by competing bass instruments.
This is one of the reasons I find recording guitar so unsatisfying; I want the recordings to sound like what my guitar amps pushing air in the room feels like. If I succeed, the mix turns to mush.
Try using far less gain on your guitars when recording. Gain that sounds great in-room is too much for a record, generally.
The great challenge of recording is to capture the authority of a roaring guitar amp, the brashness of drums, the purity of a voice, and then squeeze it down into something that fits in an iPhone earbud and still has realistic proportions. That's why the idea of "accuracy" in recording is so ludicrous. A record is to a live performance as a HO train set is to a real train. It's a miniature, a model. To make it look "right", you have to exaggerate some details and lose others.
Beyond that, with a few exceptions, most of the signal rolled off by the switch is stuff you don't want to hear anyways - "plosive" pops, rumble from low-frequency buildup in rooms, vibration, etc. Much of it can't even be reproduced by most speakers (speakers don't do low bass because, as said before, it's a hard problem and not actually audible in most cases).
As an aside, when mixing records, I'll often roll off guitars at 200 or 300hz, losing a couple of octaves of low-frequency information. In theory, this is awful. And if you listen to the solo guitar tracks, it's awful. But in an actual mix, it's great! It gets the low end of the guitars out of the way of real low-frequency instruments like bass and kick drums, making the bass sound tighter and cleaner. The guitars sound clearer too, because they aren't getting muddied by competing bass instruments.