Well there is a reason, Jim. A larger color space will give more colors and detail than the smaller color space. sRGB is used by labs so most people are not even aware of the larger color spaces. I use my printer for fine art prints these days, but when I used them for my agility shots they were hands down better than lab prints... brighter, clearer, more detail than lab prints.

I understand now, James, why you wouldn't use RGB and yes commerical labs use the smaller color gamut. My printer uses pigment inks and are archival as well as the fine art paper I use. There is, though, a huge difference between sRBG and Adobe RGB and ProPhoto color space.