Anyone from United Kingdom? a question for you only

So im an expat living in UK. I have lived in England for 6 years. To this day i have been innumerous times asked a certain question-
"(you have an accent) WHERE DO YOU COME FROM?"
I wanted to ask you -why do you think people asking this question, maybe you yourself asked it. Why?

I will tell you why im asking. Im tired of answering it. For all these years I have answered it to anyone who asks.
True, its absolutely normal and sometimes actually quite makes sense to answer it.
But, people ask sometimes even before saying hi. a hairdresser, a masseuse, person who you had a smallest of talks with,
basically almost total strangers and customer service personnel. And the reaction is 90% the same. A drawn out "aaah a .........." (my nationality) in a kind of strange tone and then creepy silence until someone will break it.

It became finally boring and i dont feel right about it. Besides, as a citizen of UK i do not want to be asked constantly where im from. I live here and they basically do not need this information. If they asked it to decipher whether they may know my language -this is not the case as not one of them ever knew it. At best they would know one word and say some corny joke. but its 10% cases. normally again 90% is that drawn eerie phrase.

Sure, first it came to the point where i began to answer automatically, robotic and uninterested, and now to the point when most of the times i will be refusing to reply. Ive been experimenting with it: replies that im from a random country didnt make me feel good though some people beieved it, replies that i am from Uk would get a reaction like "ah sure you are" and people would take me as im lying that im born here and generally cant be trusted (even people from service industry had guts to call me out on it, sadly), i tried to refuse to answer with an explanation and was called a freak.

I simply do not see the need of the majority of them to know it. I live and work here and im citizen. I do answer the question when I see it is absolutely important or when I can sense it might be necessitated by some circumstances or with deeper connection. Job collegues, somebody who i go out with, etc and some genuinely friendly people who look like they could be interested in culture, and it normally works well well, so for the right reasons to the positive cases i do reply.

So i may be missing on something because it is pretty common. Is it just polite small talk, common non mattering stuff? Do i break some unwritten code of conduct when im withholding my personal information (especially to almost total strangers)?

Is there a way to gracefully and politely decline answering such questions as psychologically it is detrimental to me. I have heard to many weird reactions ,too many same stereotypical jokes.

I am white Christian, working, not on benefits, i dont hate anyone. Though i would say i am from a country most British people have negative view on. Maybe you guessed it.

I will conclude by saying- ive seeked guidance from my fellow people how to deflect the question.
It was sort of funny although i think most of the advice wouldnt quite right pass here in UK (not one i have tried yet):
1) from planet Earth
2)from Eurasia
3)If i tell you I will have to kill you
4)wear a hammer as a pendant they will be afraid to ask
5)change topic to weather if that doesnt work then say "im not local but i have lived long here"
6)say "im from abroad" and if questioned on, wave at random direction and say "from there"

Thanks for attention, im waiting for unbigoted friendly xenophobia free replies only thank you very much