The letters have many uses, such as describing different brain states, to indicate parameters in math, or just as an alternate way to count. If you want to know more, read the Wikipedia article.
My personal use of βeta references the nickname(Pentathalos being another)given to Eratosthenes by his contemporaries. The man seemed to excel at whatever he tried but, would rarely take the gold.
Coming in second all the time in a wide number of disciplines is no mean feat, and an example I wish to emulate(winning is over rated). So, that's it. Hope I solved the mystery for you.