Okay, so here's why it's not irrelevant:
IE5 is still IE. Microsoft has an obligation to make it look good (so dumb users don't bunk newer versions in with it) and browers have the same issue (Well i'm using the internet explorer so why isn't it working?)
This same perception (which I can absolutely assure you as someone who has supported older users does happen) Is not a perception that happens with different products altogether. If you're using Netscape, they'd just tell you to use IE. If you're using Firefox, they'd just tell you it was made with "Google" in mind.
Using an example where the two products are in fact different versions of the same product is a significant difference.
But still in regards to the argument about revenue, the gaming market is constantly showing that companies will definitely implement DRM under the assumption that it is providing them revenue, even if they lose customers because of it.