I've never understood that logic. Reserves don't take food out of the mouths of AD
On the aviation side, Reservists can be seen as taking flight time away from the AC people when it's an augmented unit. There are times that does happen, especially if the Sked writers haven't been educated on the overall value and process of effectively augmenting Reservists. But if the schedule writer can take one step back from their tiny day+1 myopic world, they'll start to see the value...especially on Grad School or JPME days.
I've usually found OpsOs "get it" pretty quick, but it was the new schedule writers that initially wouldn't. This can be made even worse if it's a new unit (like a fleet SAU). I think because the RC has been at the TRACOM for so long, and there's so many flight hours to go around, it's a non-issue there.
As an aside, this isn't specific to Reservists. I ran into the same thing at the FRS as a Wing Staff IP guy (who happened to be a TAR, but that wasn't the issue). The CO and the OpsO would welcome my help, but the schedule writers (especially the new ones) wouldn't work to keep me current even when I would try to be as flexible as I could. Once skeds realized they could cold call me to fill in a spot, they realized it made their life easier and I'd be getting calls several times a week asking for help. And eventually, just calls trying to give me a good deal hookup flight because I wasn't a douche JOPA.