Same reason there isn't one that starts with an A or B or any other letter of the alphabet that doesn't go at the beginning of a number!
Today's numbers, also called Hindu-Arabic numbers, are a combination of just 10 symbols or digits: 1, 2, 3, 4, 5, 6, 7, 8, 9, and 0. These digits were introduced in Europe within the XII century by Leonardo Pisano (aka Fibonacci), an Italian mathematician. L. Pisano was educated in North Africa, where he learned and later carried to Italy the now popular Hindu-Arabic numerals.
Hindu numeral system is a pure place-value system, that is why you need a zero. Only the Hindus, within the context of Indo-European civilisations, have consistently used a zero. The Arabs, however, played an essential part in the dissemination of this numeral system.
Learn more about the origins of the numerals at www.archimedes-lab.org.
Of interest, you know the alphabet. It’s one of the first things you’re taught in school. But did you know that they’re not teaching you all of the alphabet?
There are quite a few letters we tossed aside as our language grew, and you probably never even knew they existed. Here are 12 letters that didn't make the alphabet from Mental Floss.