We don't like our pride hurt...especially since we keep losing dogfights to the Indians. 
If you'd check the rules of engagement, you'd find the war games with India are meant to show the USAF needs a bigger budget for F-22's.
story"–“The exercise, in which US F-15Cs were said to have been defeated more than 90 per cent of the time in direct combat exercises against the IAF, is causing US Air Force officials to re-evaluate the way the service trains its fighter pilots while bolstering the case for buying the F/A-22 as a way to ensure continued air dominance for the United States.”"
...
"In Cope Thunder, four F-15Cs were pitted against 10 or 12 of same model Indian fighters such as the Mirage 2000, MIG-27 and MIG-29s in offensive and defensive counter air scenarios. But the two most formidable IAF aircraft proved to be the MIG-21 Bison, an upgraded version of the Russian-made baseline MIG-21, and the Sukhoi SU-30K Flanker, US officials said."
...
""The major takeaway for the Air Force is that our prediction of needing to replace the F-15 with the F/A-22 is proving out as we get smarter and smarter about other [countries'] capabilities around the world and what technology is limited to in the F-15 airframe," Col. Snodgrass said. "We've taken [the F-15] about as far as we can and it's now time to move to the next generation." "
I've also read somewhere (can't find the source) that the F-15's were limited to AIM-7 Sparrows and onboard sensors, and the Indians could cheat- the AWACS which was acting as a referee gave India radar support, and they were free to use their whole arsenal.
