Before the Virgin merger, AA and AS complemented each other better, with the AA partnership enabling/encouraging those not located at airports with significant AS service to redeem AS awards more easily, although this was somewhat limited by the one partner per award rule. Now AA can still play this role, but it's much less necessary for those at airports with significant legacy Virgin service, so the percentage of potential customers/FFers who would be impacted in a major way in terms of the network by the loss of AA awards has become much smaller. In other words, the AS FF program needs AA less now for award tickets. OTOH AS might not be very enthusiastic to have FF participants who mostly fly AA, credit to AS, and redeem AS miles, while those who do the same from other carriers are more likely to be dispersed across airlines and credit miles from multiple carriers to AS. I can envision AS wanting to reduce its partnership ties to AA.

OTOH, since the AA/US merger, AA has had less need of AS to enhance AA's network. Even with the new Virgin routes, this is probably still true on balance as the Vrigin routes were generally already covered by AA/US. So on balance, there's also less incentive for AA to continue a strong partnership with AS.