In order to find the one trading strategy that will bring the maximum profit, it is necessary to test many trading strategies. And even when you have found the only trading strategy that you think suits you, you should not focus on it, but continue to test new strategies.
I don't think they need to test new strategies as long as the ones they're using are still good and profitable. I wouldn't force myself to use a different strategy if I was already profitable with the same one - but it might require some adjustments over time. The change of strategy is necessary if the previous strategy is no longer profitable - maintaining it will only be detrimental.
After all, in trading one does not need to chase the maximum profit, it is enough to take profits consistently at a predetermined percentage. This kind of trading approach will not put traders under pressure due to uncertain price volatility.