The strict purity rule also applies to who can perform services at the Tabernacle. Normally, male descendants of Aaron get to enter the family business. However, descendants found to be defective in some way can't be priests.
That means no blemish allowed: no little people, no blind guys, no guys in wheelchairs, and no man with a skin problem, scoliosis, smushed nose or—everyone's favorite—crushed testicles.
For such a man as this to enter into the Tabernacle would be to make a holy place ordinary, and God can't have that, can he?