I often go by my middle name, because my first name sucks and my middle name doesn’t. (IMO–no offence to any other Scotts on the board.) I don’t usually include my first initial when I do that, though …
I always guessed it was for one of two reasons:
-Their first name was something boring and plain like “John” while their middle name was more distinctive and they wanted that to be the one that people remembered.
-Their first name was something they found intolerably weird or old-fashioned and the middle name was less so, like “Clostridium Peter Hughes” or “Schenectady Michael Williams.”
My husband’s family could not be called wealthy (it’s the opposite) but this is his situation–and why he goes by his middle name and signs himself A. Middle Last.
IME usually it’s because the person got stuck with a first name like Malcolm or Wilberforce and wants to be called Bill.
My impression is that there are a lot of prominent Mormons that do this. Three of the Quorum of the Twelve list their names like that, for example.
I read the mouseover for this and thought, “Hey, wait a minute! My brother does this and he’s not rich!”
But he is an attorney.
And he’s Mormon (but he converted! After he’d already been doing the first initial thing!)
He does it because his first name is his father’s name and he’s always gone by his middle name. His son is in the same situation - his first name is my brother’s name and he goes by his middle name.
Being known as Pierpont is much cooler than just being ‘John Morgan’.
I am decidedly not wealthy.
My first name is “Cecil” and I’m a Junior.
My parents called me by my middle name so that folks knew whether they were referring to me or my Father, and other kids teased me unmercifully about Cecil the Sea Sick Sea Serpent. 
But I digress.
I use C. Middle Last as my signature, and go by Middle Last.
Yeah, I think this is true. I would say that about 20% of my students (at a public university in smalltown Mississippi, so most of them are by no means rich) go by their middle names, but I can think of only two who use the first initial. The rest of them just sign their papers “Kate Jones” or whatever, and it’s only when I go to enter grades that I get any reminder that Kate was actually christened Mary.
If this was a rich people thing, you’d think that Hamish’s bank would have gone into a bit less of a meltdown because he does it. (He is also distinctly not what you’d call rich.)
So, I’ve always been kind of confused by this. If I am calling (or emailing) someone I don’t know, whose name is listed as Q. Stuart Wadsworth, am I supposed to ask for “Stuart” or “Q”? I know I could ask for “Mr. Wadsworth” but for the sake of discussion, let’s say this is a situation where that would seem strangely formal.
I hate my first name, so I took my first and middle name and smooshed it together at about the age of 12. I wish I would’ve thought of this - C. Pained Doper. I rather like it!
I’d use Q. Stuart. As someone who has a first initial, I’d be happy with that or Stuart. Hell, it’s my fault, I gotta live with it.
My dad did this because he had the same first name as his dad. I have the same first name as both of them, and go by it. We are not rich.
D. Not Taunt
Three examples from my decidedly not rich family:
F-i-l had the same name as his father did it to lessen mix-ups.
My grandfather’s name was chosen to honor a relative, in the Jewish tradition. The Hebrew name mattered to his parents. The anglicized name didn’t. On his birth certificate his name is given as G. Herschel Krustofski*. He went all the way through school being called Herschel or Hersch. When he got a fancy job with a large company and was going to have business cards they would not allow that format and asked what the G. was for. They weren’t grooving on the jewishness of that so he just picked a G name, and went by that for the rest of his life.
An aunt, whose middle name is a family surname, but is also not uncommon as a male first name, found she had more success getting articles published that she submitted under the name “F. Middle Last” than under “First M. Last”.
*More accurate to say it was G. Herschel Krusty. The family emigrated from Poland to England before any of them came to the US. The surname was anglicized before they got here.
And if professional people do it, then nonprofessionals who are trying to be formal will do it.
What I wonder is what they did back on forms and stuff in school where the assumption is that the initial is for the middle name. Especially on those “scantrons” that only gave you one spot for your middle name. Do they reverse their name, or do they, in that one instance, actually used First M. Last?
I am far from rich, but I am formally D. Lawrence [Surname] for no other reason than that I have been called by middle name for my entire life, and it makes it easier to skip the “nobody calls me that” conversation which gets a bit tedious after 5,000 times or so.
I know a person who goes by something along the lines of R. Jehosaphat Jingleheimer. He’s as distinctive (in both appearance and personality) as his name, and I imagine that the R stands for something “boring” like “Robert.” “Jehosaphat” suits him much better.
I wrote my middle name in the first name field and ignored the initial.
The only people I know who do it actively dislike their first names, but don’t want the bother of changing their names.
I do it sometimes, too, because my middle name has more authority, and I’m hyphenated in some databases.
My first name starts with a “P”. I like my first name, but I don’t think I’d be respected in the workplace going by my first name so I have everyone call me by my middle name which is Ann. Everything I sign is “P. Ann Ostine” and my badge says “Ann” on it.