I'll take the unpopular opinion here... it actually is a problem for an adult to be dependent on their family, even if they're doing something noble with their life. It gives their family an extreme amount of control over them, that flow of money can be a powerful thing.

For example, say the BF gets a great job 1,000 miles away. She wants to move, but her family says no, we need you here... we'll cut off the money if you move. Or suppose they have kids and want to raise them without a religion, and the parents insist on taking them to church each Sunday and making them get baptized whether they want to or not. These are relatively common things parents want... it sucks ordinarily, but if the parent can lord that money over you? It's much worse.

Now, probably OP can resist that at 26. But as you age and become less able to start a new career, your expenses rise (medical, kids, lifestyle creep, etc.) so it's quite possible that if someone has never worked and they're in their late 30s, they are entirely dependent on that family money... personally, I would be really reluctant to get into a lifelong relationship with someone whose family quite possibly could be making our decisions for us.

Of course that's not an excuse for him belittling what she does with her volunteering... but there is a valid concern here potentially.