If you've used to other apps that utilize an envelope system, like YNAB or Everydollar, you may have realized that there is no option to add due dates unless you add them to your transactions.
Everyone has their own budgeting style, and one person's budget categories, or "envelopes", might be set up and named entirely different from everyone else's. If you prefer to split your categories up by name instead of a general summary ("Verizon" and "FabFitFun" instead of "Internet" and "Subscriptions" for example), you may want to know when to expect that expense by.
Check forums or subreddits for the aforementioned apps and you'll find users coming up with workarounds such as putting the due date in the category title. Why not just include a due date feature?
With Budgetwise, you will be able to set an optional due date if you'd like, to any category. Keeping it separate from the title opens it up to a whole lot more flexibility. You'll be able to edit the date much easier, see credit card due dates with a quick glance, and better manage expenses that may occur on different days each month such as car payments.