The answer to your question, you have aluded to it yourself.... By supporting the event, PFK would be contributing to the hobby, developing interest of more people and doing the right thing. This in turn would improve (some) peoples opinion of them. It might increase circulation (they are forever throwing gifts at their potential readers to subscribe, why then not offer a discount to the event upon showing a coupon in the magazine. That could increase circulation ! Its a shame that so many people think "what do I get out of it" in order to do something in the first place and your post highlights that perfectly. But I would have thought it was a no brainer that to support such events and to advertise them (advertising on the part of a magazine costs them nothing) would be of benefit to whoever does so. Otherwise why do UKAPS support it ? Simple. To increase awareness of our hobby and hopefully get more people interested. If UKAPS can do it, then Im damn sure PFK can, given that they are part of a rather large publicity house.
Anyway, I personally do not know for sure if they did not support the event, Im going by what someone else has said, but at the end of the day, if they didn't its a poor show.