No, Inkjet printers do not use steganography, but a good deal of Laser do, but not all.
As en example, I had a run of brochures done a few months ago by a print company that use a Xerox DocuColour 800 laser based machine, and you could clearly make out the yellow dots in the right light. (also my office Dell 1320c, which is a Xerox system does it)
I then had a run done by another company who use a HP Indigo press (ink based) system, which did not have visible steganography.
it very, very minimally effects the image but not much at all.
The reason is for document traceability, it is assumed that inkjet printers will not be used to print off large reams of documentation in an office environment.