The other problem is that not a single airliner kit I've ever seen (and I've owned just about every one ever made at some point) has the windows molded in the correct size, shape, and especially proper spacing. Some are better than others, but most are pretty bad. Window decals (at least the ones I draw) are done from manufacturer specs, with the correct size, shape, and spacing for the specific type of aircraft they're designed for.
There's an ongoing debate over the "best" kind of airliner window decals - the plain dark grey, or the "realistic" ones with passengers and window shades visible. I'm very much in the former camp, but lots of people like the latter style. Just a matter of preference.