There are many places in the game where number of soldiers is important, or more important than quality. Takeovers, looting, civil work and many others. Cheap units that you can mass-recruit have always had a place, and the best advise in my book was the one telling you to look for what the realm already has and try to cover out what it doesn't.
trouble is... for the big ass units, you might actually want really really crap ones. so you end up aiming for really good centres... and accepting really crap ones.
the rest that are not good enough and not crap enough you end up ditching.
range is probably not the determining factor. if you get a really good equipment one, you'll keep it even if it's r3 rather than r4. the r2 ones (is there r1 archer?!) would be a bit more iffy...
