Actually, Apple is the largest retailer of music. Also, they are doing their best to become the most important distributor for TV, Movies and eBooks. Apple sells about $5B per year in thru the iTunes Music/Apps/Movies/TV/Books Store and those sales are growing at about 25% per year. While that's only about 7% of their sales right now, it's growing steadily and likely to be about as profitable as the hardware businesses. It's also likely to equal or outstrip Mac sales within a year or two.
No, Apple is not primarily a distributor, but they are in line to become the biggest distributor. That scares the distribution competition because Apple can afford push down distribution margins to promote high-margin device sales. So, you're right they don't need the money from iTMS but iPhones and iPods and iPads aren't nearly as attractive without iTMS--that's part of what you buy when you buy the device.
And that's the difference. Intel doesn't NEED McAfee, whereas Apple can't really operate without iTMS. Intel might find a way to differentiate future processors by adding industrial-strength security to their chips by integrating AV and management suite facilities with specialized hardware, but Intel has always benefited from being the premiere supplier of open-platform technologies and they are forced to be that way both by the market and by regulation. If they change that significantly to increase margins, they may become vulnerable to attack on both fronts. To me, $8Bn is just too much for McAfee. I think they could have got the same capabilities for a lot less money. McAfee sells low-margin, crappy AV software. They earn a few hundred million a year. Intel earns 4x the return on investment in its existing business (relative to McAfee). Also, I believe the embarrassing products McAfee sells will dilute Intel's brand. In the words of Warren Buffett, as an INTC shareholder "I feel poorer".