I routinely make a dozen solutions, of varying volumes, from 30, to 33, to 37, to 53 mL. As was said, they don't make flasks in 1 mL increments. My reagents cost hundreds of dollars a gram, and react with moisture and oxygen -- I can't make 100 mL, use 33 mL, and keep them for a month or discard 64 mL.