HUMANS are not logical, that's why there are addicts and lenses are an addiction that's why we buy them, not that we need them, because there available, manufactures know this, that's whey they make so many
I'm an addict too with 25 system lenses in total (I have a few camera's with fixed lenses too but I'm not counting those).
Other lenses I own in addition to those listed in my signature (all Canon FL & FD mount):
Vivitar C/FD 28mm f/2.8 Auto Wide Angle
Canon FDn 28mm f/2.8
Canon FL 50mm f/1.8 II
Canon FL 50mm f/1.8 II (yes I have two of these and FT-QL bodies to match)
Canon FDn 50mm f/1.8
Canon FL 50mm f/3.5 Macro
Canon FL 135mm f/2.5
Canon FD 200mm f/4 S.S.C.
Of course all of these can be adapted for use on my Sony NEX, but the Macro lens is the one that remains fixed to the adapter most of the time because it is also the dedicated macro lens for my NEX system.
Come to think of it I own six
..and 7 zooms, so that means 18 primes