This was partially because the UI has a lot of issues (especially the bank statement importing - if you don't do everything just right, you have to redo it from scratch, and it is very easy to make it fail), and partially because the ability to automatically assign transactions to categories was too limited (it expects the reference to match exactly, but in many cases it doesn't, so I would have to spend a lot of time manually assigning things to categories, again from a really bad UI).
I have to add, this was 5-6 years ago, so it's possible that the UI has improved since then.