Sometimes the prediction site is needed when in an unfamiliar match because if the match is popular maybe I already know a little from my own knowledge while understanding the existing match then the prediction site is not fully relied on even though it can help you make a bet.
Well in a match anything can change even if you already know the strategy, but when during the match someone is injured or goes out due to a red card then it can change the game from attacking to depressed because this is clearly beyond prediction.
They are helpful but not necessary; they don't by any means provide a 100% accurate prediction, which is reasonable; thus, they cannot be called necessary by any means. I've had my fair share of luck in the past, but that doesn't mean much; I already had something similar in mind when betting on those matches. Such websites can be helpful tools to provide some insight; you'll get a few successes, but that doesn't truly mean much. Don't bet your chances on someone else, and don't take their word for it; they're just speculations, just like in crypto.