I think there may be some confusion here,
- Note that there are "geostationary satellites, and then other satellites." GEO satellites are, of course, entirely and totally about being on the equator. The term "geostationary satellite" implies "equatorial satellite".
I suspect there is simply a misreading of the data/images you present.
All I see in the images presented, is: "a big pile of satellites, distributed all over the globe - and of course one image shows our bunch of equatorial satellites."
Note that GPS in particular (and all the other nav constellations - GLONASS, GALILEO, etc etc) are very much evenly distributed around the globe; that's the whole point. (GPS works - in general terms - identically at the poles or anywhere else: you can see about 9 GPS satellites, at any instant, from any point at all on the ball of the Earth.)
(You can see this instantly on any awesome "Boy's Own" page about GPS satellites. Example, look at this natty animation someone bothered making, which you can find simply on the Wikipedia page for GPS.)
So again: of course, certainly and obviously, all of our "equatorial satellites" are of course … equatorial. But that's a separate category.
Regarding "all the rest", I for one don't know if there's a preference for:
(A) sort of wobbly (from our point of view) orbits (which do not go over the poles and stay somewhat near the equator); versus
(B) all-over-the-place orbits (like GPS); versus
(C) orbits that specifically go over and stay over the two poles (there would certainly be some specialized need for that - which I don't know).
(Actually, this being the age of the internet, I was able to instantly find out that Iridium, for instance, uses pure polar orbits.)
Again to repeat. You may be misreading those images. All I see is a completely random even distribution (as you would expect); plus of course one image showing all our equatorial satellites.
Just to be absolutely clear, you ask in large letters:
You ask "Why do so many of our satellites orbit at or near the equator, and why do so few pass over the poles? Is it simply a matter of "No one is there, so they don't need communications, GPS, or observation?"
Actually GPS works flawlessly at every single point on Earth equally, very much including the two poles.
You mention communication. Regarding satellite phones, funnily enough our planet's satellite phone network (Iridium), is indeed … a set of polar satellites!
Regarding "observation" — funnily enough, it appears that observational satellites do indeed tend to be polar satellites! (Wikipedia says "To get (nearly) global coverage with a low orbit it must be a polar orbit or nearly so…", you can read all about it there.)
Regarding the equator: don't forget all geostationary satellites are (of course) equatorial; that's a special group.
Again, all I see in the images is that there's completely random and even coverage, plus, the equatorial satellites.