America Medial Association, AARP (retired people) are NGOs, they advocate for their causes, that's perfectly reasonable and normal.
They are not 'for profit' obviously, and they're not strictly charities.
People can group together and organize as they please. Donations to NGOs are not tax deductible.
2) We have different regulations for different types of institutions
3) NGOs specifically exist to get around those regulations
4) A lobbying group (AARP) should have specific rules around how it can function. Lumping them with a professional standards organization makes it impossible to have reasonable anti-corruption laws. That's why NGOs exist, to make it impossible to enforce corruption laws. There is literally no other reason for it to exist as a category. We already have categories for lobbying groups and professional groups and charities.