Interesting thread. But a few things I see differently.

I come across a lot of F#s in songs - anything where the progression goes I III in D or I VI II V in A has an F# in it. The first is a pretty common blues thing (some versions of Cocaine Blues and Nobody Knows has already been mentioned) and would also occur in any song where it's used on the way to the relative minor (Hallelujah by Leonard Cohen) I III vi. American Song by Paul Simon which is straight out of Bach has the III chord in it a lot (or III7). The I VI II V is in oodles of things from Alices Restaurant to Ain't Nobodys Business if I Do)
Don is spot on when he says that the keys chosen for the songs (eg C G) decide which other chords you'll see - an E chord in a song in C would seem much more 'normal' than an F# chord just due to its familiarity (and ease of playing for many).

"I don't know if there have been, but in my experience, most published songs are too high. "

I have two thoughts on this - one on church music, one on popular music.
Most carols DO just about fit with the range of men's voices - though some do push it to the edges of its range; usually the point when you hear someone drop an octave to keep the tune! If the most common voice for a man is a baritone range (F2 - E4; the E above middle C) then there are few carols where the highest note normally printed in hymn books are outside of that range; Hark the Herald Angels traditionally has an E4 as it's top note if I remember back over the years (I think it actually is printed E3 but men will sing an octave under). A man's tenor voice is usually quoted as C3 to A4 (or C5) which makes it easily within range.
On popular song I reckon it reflects the sort of voice that catches the ear and I would guess that a lot of the voices that sing pop music tend towards the tenor range (don't mention Frank Sinatra or Bing Crosby I know they aren't tenors). As tunes are often published in the original key that the song was made a "hit" in they tend to be pitched at the high end of things. Elton John, Freddie Mercury, Sting are a few huge selling artists who come to mind.

"I have found that my friends and neighbors really like them low. Even people who think they cannot sing will join in."
I was late to take up singing (50+) and felt very self-conscious singing at the upper end of my voice because it sounded 'funny' to me and not like my usual voice. I would guess that others are similarly affected and do not wish to draw attention to themselves. The reality is usually that it sounds stranger to yourself until you get used to it than it probably does to others. (As an aside, the strange noise I used to find odd in churches when I occasionally went to them was the exaggerated slow vibrato effect - approaching yodelling and not unlike how a sheep would sing if it had the chance - which seemed to sometimes come from old ladies)

"Very few people can sing a range of two octaves. Most are happy with about one and a half max."
"Another factor is that the voice tends to drop a bit as you get older."
I don't think that I'd agree with either of those. I reckon pretty much anyone can sing two octaves. Most songs don't have a range anything like that.
I'm not a great singer but I enjoy it now having shied away from it for the first 50+ years of my life. As I have started to explore it and see what it can do (I'm only really just beginning) I realise it is a hugely more flexible instrument than I ever knew. It's range continues to expand and though I don't know how to use some of that range (yet) and some of it sounds odd I enjoy experimenting with it. My wife and I recently started having a singing lesson now and again and our teacher is very much in that vein of exploring the wonderful range of sound that you can produce (she is a great expressive singer herself).

When I started singing I would reckon that the range of my voice would go from about a low D (D2) to about C4 and the C felt a struggle so I would sing under that. I would never do it in public but I can sing up to a C5 now but without any consistency - G4 is comfortable now and I would sing it in a song, A4 is reachable. I only found the last few notes getting frustrated that I couldn't sing All Right Now in it's original key and then trying to sing Mrs Jones and Me by Counting Crows and the odd Crowded House song. But I'd pitch them both quite a bit down if I did them to be comfortable.

The tricky bit is getting a consistent sound across the different part of my voice but I'm working on that. And it will help when I start breathing :)!!

Not trying to be a smart ass here but with some practice one can radically improve ones voice. I tend to think it's more the inner fears that one has about the sound of ones own voice that is the limiting thing rather than the voice itself which is much more capable than many people think. At least in my case it does more than I thought it did when it was just sitting there unused in its box. (Sorry it's a terrible pun that just tempted me)