Fish Tank Problem. Save my Tiger Barbs!?

I have owned a goldfish for three years and never have tested nitrate, Ph, or anything like that and he's still alive , I also have 6 barbs that are fine and have never tested those things I think it's just a gimic to sell more stuff you don't really need , A fish in the wild doesn't need stuff like that so why should pet ones need it? I know the only thing I have needed was aquarium salt and chlorine reducer because all of our tap water has chlorine in it and in the wild it doesn't thats the reason you really need the chlorine reducer. but thats just how I have managed and my fish aren't dead , but don't take my word for it it's just my answer, and the pet store doesn't know what their talking about just because you vac your tank will not kill your fish, (must have been a pet smart who told you that) I worked for a pet smart as a cashire and knoew more than the pet care people did about fish, customers were bringing in dead fish left and right because the pet care employees did not tell them the right things they said all of this water quality stuff to the customers but they still braught their fish back DEAD. I had to help several customers with buying fish and not one of them braught a dead fish back that I sold.