Why do airlines think alliances are so important?

I've noticed that airlines really think alliances are important. But as a passenger, do I really care? They must think it's important enough to send me this email.

Dear Mr. Bliss,

In June 2008, Continental announced plans for extensive commercial cooperation with United Airlines and Star Alliance, linking our networks and services worldwide to deliver new benefits to our customers...blah blah blah

OnePass Members:

  • Will continue to earn OnePass miles on Delta Air Lines and Northwest Airlines for all qualifying flights through Oct. 24, 2009.
  • May book and ticket reward travel using OnePass miles for travel on Delta Air Lines and Northwest Airlines through Oct. 24, 2009.
  • Must complete all reward travel on or before Oct. 24, 2010.
  • Will continue to receive Elite upgrade privileges on Northwest through Oct. 24, 2009, or the date of the Delta SkyMiles and Northwest WorldPerks loyalty program integration, whichever comes earlier.

OK. Now what? How am I actually benefiting from this? There seems to be a lot of date restrictions and of mentions of "rewards" and "privileges". Can I click on something? Can I do anything with this email? Oh! I know. I can delete it.

A better email from Continental would have been:

Hey Chance,

We noticed that you have not arrived on-time for your pass 3 flights with Continental. Sorry about that and the sits next to the smelly toliets. As I token of our appreciation for choosing Continental, we automatically added 10,000 miles to your OnePass membership.

Book a flight with your OnePass miles now!

Happy flying,