Not volatility, but relative or correlated volatility, or correlation to the general market. Some call it a measure of risk, or an indication of whether or not you can hedged away the risk of that stock by diversifying in the rest of the market.
That is – if you buy 10 stocks all with a beta of 1, you aren’t really diversified at all.
To answer your question – not many people pay attention to it. Professionals do.
