They are the one buying and selling it for profit that provides financial support to the project owners itself. And also, traders are the one responsible for a healthy buy and sell type of investment, meaning if there are more traders in a certain type of market the better that market is. So i think more trader is better.
more traders might bring this market down . some traders only want benefits from other coins that's why they are holding their coins and then trade it when they think they can get a high profit