Official comment
I hear you. However, this is more complicated than you think it is.
For starters, what happens when a contact has more than one open order? That ruins next charge, last charge, next charge amt, as well as reminders around those dates.
Not sure what info you want from the open order report, but rollup fields (coming soon) will prob get you that.
As for cancels, you should def create signup and cancel date fields and use automation to populate those.
Fortunately, you have an incredibly powerful platform at your fingertips that allows you to do any of these things, rather than stopping you because 'it's not a built-in feature'.
The "real" solution here would be to make open orders a full-on object with automations and messages and everything. But that's complicated, and would overwhelm many users...