You use Prime or water conditioner to get rid of chlorine or chloramines. You can use Prime to bind toxic ammonia and turn it into non-toxic ammonium if you have ammonia in your well water.
Not many people on well water use Prime or any water conditioner because most well water does not have chlorine/chloramines.
I have well water and don’t really use it. I’ll occasionally use it for my reef tank just to be sure but haven’t really worried about it for freshwater.