How important wards are

Go into my match history and click the fizz game where i was 7/7/4, it was a ranked 5's. no one bought any wards at all and never upgraded there trinket, i did the bare minimum and place 10 more wards then the support. I had the least deaths in the game btw which is it coincidence? maybe. They claimed after it was a privilege for me to play with them... they are gold and silver as i am bronze but climbing fast, and then at the end of the game they said it would have been any different if we didn't buy wards. Maybe true, but the person who said it was the ekko and i saw him get picked off in our jungle so many times. Now i was at first going ad fizz with frozen heart, my by team said sell all your items and go buy ap, it wasn't the best idea now that i think of it to go ad fizz especially vs a volibear, and i didn't get fed fast enough. Why are wards important and why should i buy them? why do i still play with these guys, idk.