Terms cis, why is it a thing?, for those that identify with the gender their were assigned with at birth

Just curious and wanted to see what people think, and I dont mean to offend anyone, but im going to ask this, why are straight people called cis what I means is im a male, and im straight and i was born male at birth and straight, and i identify as a man/straight, one of my friends that i have is trans and they said to me that im a cis male inothers words from what i remember they were saying im straight and a male that identify with the gender he was assigned at birth, though that is true, i did not want to be called a cis male now did i ask to be called as such because while i do identify with the gender at birth and is straight I didn't ask to be know as a cis male i only want to be known as a straight male not cis though my trans friend say ok and all but I heard a lot of other people say their cis, yet their straight at the same time and identity with their assigned gender at birth, my question is this, no one likes an assigned label to them right?, especially if they dont agree with it, now its not that I dont agree with the label of cis but I did not ask for it nor want to be known as a cis male, i just wanted to be known as straight if you will so im curious why is cis even a thing? Why not just got with the original term know as straight that is if that person identifys as straight, why call them cis?, more to the point how do I get that label of cis removed from me, I mean, i mean no disrespect to anyone who read this im mainly just curious about this cis stuff and want to learn more about it, because I am a straight male assinged at brith why do people say im cis and how do I remove that label from me, because i just wanted to be knows as straight because that is what i identity as and was assigned with at birth, either case im just curious what all this cis stuff and just wanted to what people thought about it, again I mean no disrespect or hurtfulness to anyone who reads this and i dont mean to offend anyone, im just wanted to see what people think that's all