Interesting how some onsiters feel like they're being denied a perk.
First of all, onsiters get first shot at FP+ reservations. That IS a perk, make no mistake about it. Onsiters will have a better chance of coordinating rides and ADRs. Onsiters have the chance to ride TSM at a reasonable hour (or at all), get a good spot to view Illuminations, etc.
I'm not sure how it matters to the park experience of these certain onsiters whether or not offsiters make their FP+ reservations 30 days in advance or the day of. Onsiters still had first shot at the choice attractions/times. Perhaps they feel that offsiters should suffer a little at a long kiosk line with a fustrated CM instead of enjoying their vacation. Sorta cruel, I guess.
Second, if Disney has a better idea of which attractions guests will be visiting in advance, they can staff the attractions accordingly. This has the potential to SHORTEN some of the lines.
If Disney is missing information about the majority of its guests (offfsiters), they cannot possibly staff an attraction to meet an unknown demand. Likewise, if Disney has a better idea of what the park attendance will be, they can have enough food available for everyone.
Third, this boondoggle is costing Disney a fortune. If advanced reservations for FP+ were only offered to onsite guests as an exclusive perk, then onsite guests would most likely exclusively bear the inevitable price increase.
However, since it is now available to all, the cost will be shared by all.