Does It have to be loud?

I listen at 50 to 60dB measured at listening chair.
70dB is pretty loud and I only rarely play music that loud, and 80dB peaks is as loud as I ever play music at home.(mainly opera climaxes.)
When I go to a dealer to audition they always turn it up way too loud.
I bring my phone dB meter and set it to my preferences.
People just get used to loud playing and expect it. When it is turned down they just hate it. But if you listen at lower levels all the time, your ears adjust.

A lot of not mentioned things are the type of music one likes (though a few if the recent posts DO mention what type of music being discussed in the dB comment) It is easy to have realistic volume listening to a solo artist playing an acoustic guitar. Same for piano, or even Classical chamber music at relatively low SPL
But them you have Death Metal. That expected dB is 100? Also the amount of bass. Particularly low bass, gut massage bass.. adds a LOT to the dB meter. So folks WITH a sub, or strong bass output speakers will have a higher dB than folks playing the SAME MUSIC without a sub or prodigious bass output

In large Classical, and in Opera, only the climaxes are really loud..
(thus my personal 80dB for opera climaxes)
So some of the disparity of folks playing levels is ’what they play’.
I seldom play Heavy Metal! And little Hard Rock.
The vast majority of what I play is small combo Jazz, Small scale Classical.

One other point is nothing is lost playing at lower levels with good equipment. (though when I hit the bottom, like extremely hushed passages in an orchestral piece and the music is too soft to actually hear well, yet the loudest are louder than I want to play at,, Talk about dynamic range.. But that is rare.. My latest cable upgrade made this more of a problem, though like I said, only rarely and particularly on large scale Classical.)

For dB meter.
I own a digital Radio Shack dB meter. I keep it set to "C" weighted.
I also have a smartphone app. Also set to 'C' weighted.  Comparing the two, they are very close all through the range.
(one additional problem with the RS meter is the range is 10dB, adjusted with a knob. So one has to know in advance approximately what range you are measuring, or all you get is 'high' or 'low'.
No such problem with the phone app.
The phone or meter are used at my usual seated listening position.
The difference from holding the meter or phone in my hand at a comfortable spot vs right at my ear is too small to bother about. (though for purists I would admit the ear position is about 1dB lower than just holding it (since it is another foot or so further back. But I prefer being able to SEE the meter while I am using it. LOL

The big plus with the phone app is it records the dB level over several minutes. That is something the RS meter cannot do.

Now neither one has been professionally calibrated. but are way way better than no meter...
As for "gimmicky phone app" I guess you never actually used one. No gimmicks, just a useful app. (I would say its usefulness may depend on the phone mic. But most ($800 or so) Smartphones have a decent mic.

Speaking of loud. I remember back in the 80’s.. I lived in the ’hippie punk 20something part of town. On a Saturday someone was playing something rather loud (Enough so they are at least a block away, and I could hear the music)
So I decided to crank up MY music.. Opened the windows and turned up the Figaro aria of ’Barber of Seville’ to as high as it would go..
I naturally had to plug my own ears..
I can say the entire neighborhood heard that aria with no distortion.
(From my then Infinity RSIIa powered by a pair of Carver amps.)

Then the day a next door neighbor was annoying me.. I turned up the volume to 11 and started a rock record.. The first hard hits caused my building manager (who lived directly above me) to jump up from a nap while thinking a truck had hit the apartment building. (That related to me later on while we both laughed, we were all young)

Now I am old and do not want to disturb the neighbors at all. If I want loud I listen via headphones

A comment on the dB thing and size of ’room’.
Shoot a big caliber handgun outdoors and it is kinda loud, but soundwise not a big deal. Shoot it in a bathroom or a closed car and it might blow your eardrums out. (not known from experience at all)
Same thing playing music. (think of the tiny acoustic space in earbuds...)
People are always asking how to compensate for oddball entryways in a music playback room. The opening mess up the flow of the sound pressures.
And having a big opening is almost like having a bigger room.