Because Chrome was built by the world's biggest advertising company. If the World Wildlife Fund started selling ivory to pay the bills, would that not be surprising?
That analogy doesn't really work, though: Mozilla's goal is not specifically to fight against online advertising. Ad-blocking is connected to their goals, definitely, but they clearly have to make compromises, and I'm not that surprised that they'd think about that one.
That analogy doesn't really work, though: Mozilla's goal is not specifically to fight against online advertising. Ad-blocking is connected to their goals, definitely, but they clearly have to make compromises, and I'm not that surprised that they'd think about that one.