My personal reasonings:
Just because a knob is usable to its extremes doesn't mean it should be used to its extremes, or even at all. I would "not want to take advantage of" the knobs if changing them offers no advantage. Tone is arbitrary. Tone is relative. You can sit there fiddling with the knobs all day until you achieve some mystical magical tone you like, but that tone doesn't mean anything until it's in a mix or in a room playing music.
I think my 4 string sounds fantastic in its current setup. I plug it into my amp and i think it sounds great. Cool. If i start boosting the low-mids on my amp, cool. Now it sounds great plus more low-mids. If i cut the low-mids, now it sounds great with less low-mids. Cool. I've accomplished nothing, and it means nothing. I'm just playing my bass with different EQ settings that are completely arbitrary.
If i'm recording, i leave the EQ flat because i'll be EQing the bass and every other instrument in the context of the mix. It would be silly to boost my amp's low-mids only to have to pull out the low-mids in the mix. And then once the good clean sound is in there, i can use all my plugins to do whatever crazy manipulations i might want or need.
If i'm playing with other musicians in a room, i'll wait until i hear how the bass fits in sonically with the other instruments and in the room, then adjust the EQ if i need to. If i just show up and turn the knobs to those holy "MY SOUND" settings people speak of, it might be all wrong for the room or the instrumentation or fitting in with the other instruments.
And if i'm performing live at a venue, i'll leave the EQ flat and let the Sound Engineer adjust the tone for the room out of the mains. Since i don't (won't) do live sound anymore, i'll gladly let them deal with the headache of adjusting. If they're a regular at that venue, they'll know the room better than me and adjust on the board, or ask me to adjust my EQ.
If i plug in my bass and HAVE TO use the EQ because i don't like the sound, either the bass sounds like garbage, the amp does, or the combination of the two doesn't. Case in point: My 6 string. Has active electronics on it. I essentially have the Bass, Mid, & Treble set on those the same all the time. If i used the onboard EQ to adjust for different situations as needed, cool. But leaving it set the same way all the time to make it sound good? That just means i'm compensating for the sound coming out of the pickups, which means either the strings, pickups, or both don't sound good to my ear. So i'm planning on getting new pickups for it.
And from my experience in production, engineering, and live sound, it was usually the musicians who came in, cranked their amp's dials to "their settings" for "their sound," and refused to or complained about adjusting the settings for the recording process, the mic, the song, or how it sounds in the control-room, are the same ones who complain at the end of the production process that their instrument sounds terrible in the mix. The flip side, when players came in, plugged in and then adjusted to the situation usually played great and were much easier to get great tone for the mix from.
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The flip side to your question about not using gear:
Why would you use your gear?
Say you're standing there with your bass, a pedal board with 2 different distortions, a Wah Wah, and Envelope Filter, and an octaver. Why not use all that gear, right? Say you're gonna play Etta James "At Last." You still gonna use all the gear? I'm not talking about playing a crazy space-funk-rock version of it in some experimental band. I'm saying play "At Last" straight. Why would you use all your gear? All you need is your bass and an amp, and if the bass sounds good and sits well in the mix already, why would you use the EQ on your amp too?