It takes more time than you think to implement something even as seemingly simple as this.
UI is notoriously a pain in the arse in Unity. Over the versions it has got better but its still no walk in the park. After that you have to ensure all the buttons do what they're supposed to do (takes longer than it sounds) and then check they are doing the correct things in the correct states.
Then testing to see if the buttons you have made are even viable when used in game. What if you made the buttons too small so its too hard to press in the heat of battle? Better go adjust those, then the rest of them if you aren't smart about setting up the layout.
This could go on for a while and we haven't even started on testing different resolutions yet, the point is, even something that looks like it's a tiny change to the end user, ends up being several hours of work.
Be thankful we're not huge fans of documentation, or expect the task to take at least double the amount of time
Software development can be really frickin irritating at times.
I understand what you're saying @M1_Abrams and it wont take us a month to do or anything, but finding a spare block of 3-4 hours+ is really tough and we simply have things higher on the priority list