ADS-B isn't a weather product, is it? It tells you where other planes are, it does not tell you about cloud layers, winds-aloft, or other meteorological data. Unless I'm incredibly mistaken.

SXM carries this (along with a ton of other products) in their stream, alongside the audio channels that most people know. Their agricultural products, aviation products, stock-market feed, fuel-price data, and more, are valuable to various markets who buy specialized displays with the receivers integrated into them.