Probably a couple reasons...
- According to Schoeps, "The MK 5/CCM 5 has a slight high-frequency emphasis when compared with the corresponding single-pattern MK 2/CCM 2(omni) and MK 4/CCM 4 (cardioid)."
- The price of a MK5 is only about 15% less than the price of a MK4 and an MK2. That makes the MK5 a pretty expensive capsule. I think a lot of us get capsules a little at a time. Another advantage of owning MK4 and MK2 capsules is that they can be used simultaniously (lend to another taper, multitrack, etc).
- Jason