Well, they can't do that job as we all see.

The original reason behind them establishing Mozilla Corporation over Mozilla Foundation was that they can keep this practice going while being safe from taxmen reprimanding them for pocketing what is a charity income from tax standpoint.

Now, Mozilla Corporation bills Mozilla Foundation for "service offered at a market price" to do its "socially beneficial, free of charge and any expectation of remuneration" activity, which is selling ads.