In the UK, the purpose of a tip is to reward a server for exceptional service.
Nope.
Tip definition: to give someone who has provided you with a service an extra amount of money to thank them
That's it. The rest is heresay based on personal values, opinions, stories or excuses.
So to answer Op definitively...
You never tip, you have never tipped, and you want to know if that is mean. Yes that is mean. Not mean as in unkind but mean as in stingy. You have never considered going over and above on your side of the bargain (payment) and I'd hazard a guess that in your whole life you have received service that goes over and above their side of the bargain.
There is a real misconception here about what is good service and what is the bare minimum.
Good service is everything running smoothly, or issues being resolved gracefully and promptly. That's enough to warrant a gratuity.
As to the convention of tipping - actually a red herring here. You asked if a blanket policy of not tipping is mean (stingy), implying that you can afford to tip (as you didn't mention otherwise) and the answer is yes.