Why doesn't the applicator brush reach the bottom of nail polish bottle?

"It's all because of manufacturing variations," explains Mylene Menard of cosmetics manufacturer Maybelline in New York. "A typical nail polish bottle can have four manufacturing variations."
One could be the length of the plastic applicator brush, or wand.
Another could be the hair on the wand. A third variation could lie in the thickness of the bottle and the fourth could be a very small variation in the amount of polish in the bottle.
"Since the first three parts are moulded separately, the outcomes are not always identical. For instance, the glass could be thicker or thinner, or the variation might lie in the length of the hair placed on the wand."
Often, "the only way to get the last little bit," says Menard, is to tilt the bottle," and that unfortunately can often result in spilling and sticky mess.