Don't want to sell my primes even when they are covered by my zooms.
I love my 35L and 135L, they have their place when light is getting tricky or I want to have that 1.4/2.0- look.
My 2 cents.
I agree... I have 16-35 2.8 II, 70-200 2.8 IS II, and 24-105 f/4 zooms, and I have the 28 2.8 IS, but I keep wanting bigger aperture. My only large aperture now is the 50 1.4. My 85 1.8 was damaged, and I tried a 24 1.4 several years ago but it didn't focus reliably on my 5DII. Now with the 5DIII I'm going to give the 24 1.4 another try, and I'd like a 50 1.4 IS and an 85 1.4 IS.
Large aperture primes provide opportunities for unique shots that are not possible on the zooms.