@Nesse1
between the end pieces is because of cost. The sheet metal creates a more finished appearance, compared to nothing between, and they hold the end pieces in approximately the correct position, which makes it easier to get the lathe positioned on the stand the first time.
I agree, it is all for appearance. I put casters on my PM1440GT before wheeling it into the shop room as there was very limited room to maneuver around a hall way and the door. I then put angle iron braces along the length, at the casters mounts, to hold them fixed relative to each other. I was concerned that rolling it might cause the stand to twist at the mount to the lathe. (However, this fear seems to have been unfounded.) I built all of the parts for the caster system at home and installed them at PM before taking delivery. So I measured everything first at PM. During installation I found that the two stands were not aligned (square), but were slightly twisted relative to each other. So the two long braces did not fit as well as I had hoped. After I pretty much had drilled my final holes and bolted it all together Matt (PM) came by. He mentioned that there was enough play in the lathe to stand bolt holes that I could have just loosened the lathe bolts to the two stands and rotated them a bit. Anyway, it all worked out. For placing the lathe or to work on in in the future I could/can roll it about. Once it was in its final position, I use the adjustable feet to lift it off the casters and leveled it up.
I too had thought about removing the decorative sheet metal and putting a tool cart under there. However, on the PM1440GT there is a safety foot brake lever that runs the length of the lathe that is in the way so I live with the dead space.
https://www.precisionmatthews.com/shop/pm-1440gt/ I seldom use it as my VFD conversion has the electronic brake which is pretty fast. So it could be removed. But then it is a safety thing! That foot brake cuts the power, turns on the electronic brake, and applies the mechanical brake all at the same time. The spindle stops almost instantaneously. It is impressive. Also, the debris pan under the lathe is deep and takes up quite a bit of the vertical space. It is also used to feed the cutting oil back to the pump, which is inside the tailstock stand.
By the way, those stands are made from thick sheet metal that has been roll/folded at the vertical corners into a square column and then welded. Likewise, the thicker metal at the top and bottom are welded in place. So while they are strong and pretty nice, they are not perfectly square.
Dave L.