It's always a good idea to have a budget. Setting one up can be a hassle, though.
It's easier if you can visualize your bills and expenses. You can see how much you're spending versus what you're getting paid.
If you're paying off a debt or saving for something specific, it's also great to be able to visualize your progress toward whatever you're trying to do. Numbers are one thing, but getting actual visual information can be more useful.
That's where a budget app comes in.