It's not unusual. I'm not saying it's right, but it is definitely not unusual. I have also had to wipe down the tray table multiple times because it wasn't cleaned, and I often wipe down the seat back in front of me, the centre tray etc if it's dirty (I carry Aegean J hand wipes for that very purpose - I never needed to use it that way on Aegean!).

Not just on QF though. I had to change seat on SQ, had dirty seats on CX that appalled the crew, and on BA... that's a pretty regular occurrence even in F.

It's not a justification in any way, I'm just saying it happens too often, and far too often for my liking.