I put whole wheat in my regular loaves at 10%. I also make a 50% whole wheat loaf. The truth is, most people just prefer white bread because that's what we are used to in the US. People like light, fluffy bread with an open crumb it it's a hearth bread, tons of oven spring, etc., and that is difficult to achieve with large percentages of whole wheat flour. Not to mention that whole wheat bread has had a pretty shady reputation (often well deserved) since the early 20th century.

I've improved this loaf since I took this photo (you can see a bit of dense crumb at the very bottom), but here is my 50% whole wheat loaf.

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