That does make sense, it'd help make being a feedee feel less tacked on if you could earn XP and upgrades from gaining weight yourself. I'd like players to be able to play how they want without feeling like they're missing out by doing so.
Alternative ways of making money could help, so you don't need to rely on the doughnut shop or feeder upgrades that boost money earned.
You're right that it didn't make sense to still have to pay for those events when with a feeder. One of the bug-fix updates I released this weekend addressed that, so hopefully those are showing up as free for you now (when you're there with a feeder).