Why, when free and open source alternatives exist? I don't know about you, but I'd rather donate to something like Jerboa, than spend the same amount of money supporting proprietary software. Especially as Lemmy itself is an open source protocol.
I've gotten ads for that thing too. I think it's because Google ads really only knows that you're on social media and little more so it just shoves ads for "social media" at you and then this happens. I think, at least kinda, that it's reassuring seeing ads so disconnected from my usage of the app since it implies little information is being sent to third party advertisers.
Next time I get paid I'll just pay the dev though tbh