This was not that obvious in the 1990s.
> It would be absurd for antitrust regulators to prohibit software vendors from enhancing their products just for the sake of protecting competitors' revenue.
This is absolutely a situation where a bundling case could apply, if a large incumbent uses their monopoly power in one product area to enter another and unfairly compete. IANAL but I don't believe whether or not the product was available separately or not would factor much into such a case.