I'm going to guess possibly the content? Money blogs don't really have the range they're probably looking for, not compared to sites where they can show ads for clothing, appliances, food, toys etc
If I look on my site I have ads for makeup, car insurance, holidays, clothing, Spotify and I assume it's because I cover a range of subjects or subjects they have more clients for?
Is there scope for you to branch out maybe? Start looking at Lifestyle in general rather mostly focusing on money - I know you do other things like review restaurants etc but from your homepage, I see it as mostly money related and so will their clients.