They used to. There was the
K811 some 10 years ago, which was one of the first wireless keyboards for Mac with backlight. I still use it to this day, replaced the battery once and battery life is pretty decent, I get 2-3 weeks out of it.
I don't even understand why they still stick with silver and white at all. I don't even know why Apple still does for their keyboard and mouse. They got matching colors for the iMac, but using a keyboard with a MacBook pro, the white just stands out like a sore thumb.
Fun fact - I had a wireless Apple keyboard (the one with the barrel and 2 AA batteries) and had a top shell from a broken MacBook pro (don't ever set a drink down next to it and reach for the trackpad in the dark to wake it from sleep). I thought "fine, I'll do it myself" and wanted to switch all the keys since they were exactly the same shape. Those mfers thought of that and prevented it. The mechanism on the MBP keys was rotated 90° from the ones on the bluetooth keyboard.
The lengths they went through to keep people from creating their own silver and black keyboard is really something else.