I think these are called retroviruses [1]. Not an expert but if I remember correctly, that DNA can sometimes mutate and turn into something useful and this has

I think these are called retroviruses [1]. Not an expert but if I remember correctly, that DNA can sometimes mutate and turn into something useful and this has happened before so they're not totally useless. But most of the time that DNA is inactivated, non-coding so it doesn't make any proteins. [1]https://en.wikipedia.org/wiki/Retrovirus https://en.wikipedia.org/wiki/Retrovirus