Apparently a lot of people are joking. 90+% of the equalizers I see have a smiley face display. Those few that use a microphone and measurements for setting an equalizer never have a smiley face on their Eq's.
I think I was 19 when I first acquired an equalizer. I had read about the Fletcher-Munson curves and understood that the sensitivity of human hearing drooped at the extremes, and peaked in the mids, so knowing just enough to be dangerous I set my sliders to correct for this, resulting in smiling sliders. However, I'd also read that the curve flattened somewhat (relatively) as volume went higher, so as I turned up the volume, which was often at age 19, I set the sliders toward flat, or just flat when really cranking it. I figured that was good for the speakers, too. Then I read that it is better to cut than boost, so I began using cut only, with the mid-position being my upper stop. However, I also was making less drastic cuts when I did use it - the smile became a demure one. In addition, most of the time I left it flat because I was 19 and cranking
Bloodrock, or whatever.
By the time I turned twenty, I ran into an article about room modes. Nodes, antinodes, standing waves, etc. That was when I quit eqing - I realized I had no idea how to set the darn thing that made any sense to me, and I just started listening without any tone control at all - I'd stopped using loudness long before because I thought it screwed up the sound, which is why I'd acquired the eq in the first place - to set a subtler compensation. But I can understand why the smiley face ends up used so ubiquitously.
Our audio journeys aren't all the same, and what I think, believe or do isn't carved in stone anywhere. Certainly my hearing has changed in the forty-plus years since those days. The only eqing I really do anymore is set the level for my sub, then leave it alone. And speaker placement. Using that eq, though, was a learning experience. I found what 125hz sounded like, or 8 kHz, etc. That was valuable.
Fast forward to today... I understand very well that room eqing using the modern advantages of DSP eval and correction, rather than crude analog filtering devices, is the way to go, but I'm comfortable with my old ways and don't want to buy the stuff to do it, or have to learn how to use it. Would I have an eye-opening experience if I did? Maybe, IDK. What I do know is that I enjoy music with my gear daily and making software work out of it does not appeal to me any at all, whereas building a simple dipole antenna is fun. I like fun.