An aside, photographs of keyboards are the only photos that I ever notice this. Some one took a picture of their filco and I noticed the same thing. I guess those long lines really make it pop out.
FWIW, It's most likely a result of standing over keyboards to get a proper vantage point vs. many other things being shot from the side. Being that close up, and keyboards being fairly large for macro or near macro range, the sellers probably have the lens zoomed as wide as possible and *any* zoom lens is going to show its faults at the far extents of their zoom range.
