I enjoy shooting and reloading a number of handgun cartridges: .380 Auto, 9x19, 357 Sig, .40S&W, .45ACP, .38SPL, .357Mag, .44SPL, and .44Mag. I have no desire to standardize and might expand even further into 10mm, .380 Mak, 7.62x25, and .32ACP. I don't work with as many rifle chamberings: .223 Rem, .257 Roberts, 7mm RM, 30-30, and 45-70. My next rifles will be something in 30-06 and something .308.
I recognize the economics of loading only a few cartridges, but I prefer variety and flexibility. If I am ever affected by a shortage of components of any kind, I can shift to others.