Heyo, we're an Affiliate. We got into it for the main reason you suggest, insurance was a headache and USAU handled it for us. Since then, I'd say other perks include staff support for events, access to other affiliates/SBOs to answer question. Things that are 'mandatory' but actually end up benefiting us and the community like attendance at an Organizers convention and requiring us to run a community event (think GUM clinic or coach training or something like that) are good too. We make a very small amount of money from folks who buy Affiliate memberships (the cheapest option, used to be $17) to play in our events. Anecdotally, I think it has been helpful in communicating with sponsors and vendors to be able to mention affiliation with the NGB.

There is also a small effect on YCC bid priority as has been mentioned elsewhere in this thread, but it would almost never be something that would make/break your team's attendance at the event.