I don't really understand the question (but true to form will blow some wind about it anyway
). I tune today the same way I taught myself to tune the day I bought my first pedal steel. I take an E from a harmonica, keyboard or tuning meter and tune the rest of the strings and stops by playing chords and tuning the chords to sound nice. I don't consciously count beats or search for beatless, I just tune the chord to sound in tune to my ears (which is close to beatless if I really listen). According to b0b's recent poll, that's the way 80% of steelers tune, although some people have written out a chart of where their tuning falls on a meter, so they can tune to a meter if they are in a noisy situation where they can't hear themselves tune. Some people use the one-size-sort-of-fits-all Newman tuning chart or Peterson meter presets rather than figure out their own tuning, but that is very close to the same thing.
Once I have tuned my pedal and lever stops carefully at home, they are stable for a long time, over a month. So I don't usually tune them on a gig. At the start of a gig, I check the tuning of my open strings by ear or meter (as described above). Unless I have new strings that are still stretching (I try to change them ahead of time and play them until they are stable at home), I don't usually have to retune them the rest of the night, although I might check them at the start of each set. So I don't understand what all the retuning is you refer to.
According to the poll about 20% of steelers don't mess with ear tuning, and just tune everything straight up to a meter. I would imagine that, like me, once they have done that at the start of a gig, they don't need to retune again for the rest of the night, but they might check at the beginning of each set.
But the term "tuning" has two meanings. One refers to the method of acheiving proper intonation, as in tuning to Just Intonation (JI) by ear (as described above), or tuning to Equal Temper straight up to a meter, or somewhere in between. The other meaning of tuning is the notes you set your strings and pedal and lever stops to, the copedant. There are some standard tunings, such as E9 and C6 on pedal steel, and many more on lap steel. But there are infinite variations of those standards. Why is that?
The reason is that our music is based on a chromatic scale with 12 tones to an octave. But almost none of us have 12 strings to an octave. Of course you can move the bar to play single notes and get the whole chromatic scale. But we need to be able to play two or notes at once for harmony and chords. It's a straight bar - you can't bend it. Even ignoring the chromatic accidentals, there are 8 tones to an octave for either a major or minor scale. But we don't always have 8 strings to an octave. C6 has 5 strings to an octave. The standard 10-string E9 does have 8 strings and a full major scale in its middle octave. But with those notes you can only get certain "pure" chords: I, IIm, IIIm, IV, V, VIm, and a few others, V7, Imaj7, etc. If you need more complicated chords, you need more strings, or you need pedals and levers. Also, if you need something above or below the middle octave, there are limited notes there. So to get the extra chromatic notes that are needed, people start adding more strings or more pedal and lever changes.
But few people add enough to get the whole chromatic scale. You've only got two feet and two knees. And if you end up with 8 or more strings to an octave, like a harp, they get in the way of playing chords. You'd need a bar as long as your forearm, and a picking hand two or three times bigger than most of us have. So people just add enough strings and changes to get the chords they think they need for the type of music they play. There are a lot of differences of opinions about that, so people end up with different copedants. Even for people who are after the same chords and notes, there are differences of opinion about whether to get them with strings, raises or lowers, combined with other changes or split, etc. So this leads to a lot of variety and a lot of discussion. It's only natural. You have to work out some compromise between ease of getting the oft used simple pure chords and the ease of getting more notes for more complicated chords. It is a bit unique, but there is nothing wrong with this situation, and there is nothing wrong with our instrument - it's a source of fascination for some players.
Fretless strings and horns mostly play one note at a time, and have the whole chromatic scale. So they don't have this problem. Keyboards have the whole chromatic scale also. Guitars do have a similar problem. There is a standard tuning for guitar, but there are many variations. There is drop D tuning, modal tuning, and lots of open tunings to different chords and inversions. Slide guitar players have the same problem of a straight slide, and so use a variety of open tunings.
In spite of all this variety, for a given gig, most steelers do not retune to different copedants in the middle of a gig, unless you call using pedals and levers or switching necks retuning. So I'm still not sure I understand the original question.