I think you are right that ideally there air return should be near the floor in the winter and near the ceiling in the summer.

I could see installing the air return close to the floor would present some problems. it creates a spot where you can't place furniture. I also think it would create a potential draft if you sat between a supply and return. The moving air could cause a wind chill effect.

Ask the contractor to cut a second intake near the floor. It should be easy and not cost very much. Most air returns are undersized, so a second intake will help.

"Can anyone fill me in here as to why this doesn't get done?"
Mossy,know what? That is a question to be answered on a long list of issues. It has simply become the American way because " only good enough" looks great compared to the rest of the world. Here are a few imho that demonstrate the mind set.
Automobiles have been progressivly desighned so it requires less skill to operate them. Driving a mud/ice obstical course,I wager I can maintain control and stop in less distance with abs disabled on a 100k + mile vehicle than majority of those who learned to drive abs equiped cars driving one where abs remains connected.
If you become bored and without anything fun or constructive to do,try this. Call any federal agency that supposly works exclusivly with a single day to day issue. They exist but they don't actualy do anything other than issue printed material talking about the work they don't preform.
The concept you spoke of was used in some homes built 50 years ago. A simple butterfly diverts return air flow between high and low intakes. In some floor plans,esp two story,the duct not carrying return at the time is carrying supply.

Thanks for the replies and the assurance that I'm not just imagining things.
The return would be in a hallway. So, there's no sitting next to it or anything. The spot is an old linen closet. Seems like it would be simple to convert it to hold the return and duct. The air handler is literally just above and to the side of the linen closet- in a word, perfectly placed. The current return that the hammer swingers installed is in the ceiling of the same hallway. This Wednesday, I'm supposed to meet with the contractor who installed it and hopefully he will finally listen to me and change it to how I want it.
Most returns are undersized huh? How does one determine if their return is properly sized?

Here is link which shows minimum sizes for duct work. You need about 400 CFM of air flow for each ton of AC cooling. The filter should be one square inch for each two CFM of air flow.

Here is a link that might be useful: Rules of Thumb for Duct Sizing

"The concept you spoke of was used in some homes built 50 years ago. A simple butterfly diverts return air flow between high and low intakes. In some floor plans,esp two story,the duct not carrying return at the time is carrying supply. "

Durn, that's awesome. Sounds like a smart person was kicking around somewhere at sometime. If you could provide a link to such butterfly designs, I would be very grateful.

By chance are your supply registers also in the ceiling? Possibly it means the heat pump equipment is in the attic, and it's easiest to have properly sized supply and return ducts in the ceiling. To have a return either high or low in the wall, you'd need it to be much larger than the space between a pair of wall studs, so you'd need a vertical duct between the wall the size of a small closet, robbing potentially valuable living space or closet space.

Of course if you are building your own custom house you can design the floor plan any way you want...

Filters near the floor collect debris much quicker than those in the ceiling. Whether that is good or bad is a matter of perspective.
I recently did some work on a house to convert the return intake/filter to the ceiling. The HVAC guys did the ductwork. The previous had the filter in the furnace in the crawlspace with the return grilles in the walls near the ceiling of 3 rooms. And those original returns were too small in total area. Filters are relatively easy to change on the ceiling.