Because most app users will demand bank integration so they don't have to enter anything in manually.

There are a few providers out there that have unified APIs like Plaid, Yodlee, and my favorite, MX [1]. These providers become very expensive with growth, and the app creator would lose money very quickly if not for the cost that is alleviated by the user of the app.

It's the only way to compete with the larger apps like Mint without having a boatload of money to spend (like Intuit).

[1] https://data.mx.com/products/api

Can't speak for all competition, but Predict is using third party company to securely connect to banks around the world. It would not be possible to do otherwise, and it is the main reason for subscription price.