I have worn matching underwear everyday for the last 14 years (matching colours counts, not just sets).
I like it because it makes me feel nice regardless of what I have on over the top.
The only exceptions when I broke this self imposed rule was when changing my normal bra for a sports bra.
I do feel I've missed out on some fun knickers over the years, but just couldn't bring myself to not match. Having a big bust means they don't always make my size in some designs 
Now DS has arrived it had gone out of the window as not always possible plus I couldn't get a nude bf bra before he arrived and not happened since.
When I stop bf I plan to treat myself to some new sets and return to my old habits.
Is it just me or do many people like to match and find odd undies just feel a bit wrong.