Gordon Moat wrote:

I really wonder about the longer focal length, or telephoto usage. While
many
seem to want longer lenses, I question how much they actually get used.
[...]

Many medium format (645 or 6x6 mostly) photographers will claim using a
150
mm lens often. When looking at what these are most useful for, it is often
tight framing for portraits, either head shots, or only head and shoulders
(upper torso) images. While a longer lens can be less obtrusive to your
subject, by allowing more distance, I really wonder about the desire to
always fill the frame.

It's not about being less obtrusive.

Long lenses have a far wider use than just filling a frame with a tight head
shot. Are not restricted to portrait photography.
Landscape photography, for instance, wants a rather wide lens, or a long
one; you either show the lay of the land, or details. Or produce boredom.

And that (excluding the boring bits) is what makes short tele's very useful.
I think you're assumption ("what these are most useful for [etc.]") is
severely flawed.

With 6x6 photographers especially, most of the square
images get cropped anyway, so what is the big deal about cropping further.

What do you mean, "most of the square images get cropped anyway"?

The big deal about cropping is that you don't invest in MF equipment to end
up using bits of film no larger than the 35 mm miniature format.
And it's not the money, its why you spend the money: there is quality in
square mm/inches. The more the better.