How many monthly active users does Twitter have? I mean, blocking trolls individually is certainly a way to keep busy, but ultimately useless as there are too many, and the craftier and more dangerous trolls (i.e. government sponsored) might have a blue checkmark next to their name and already in your follows list.
It also affects what the what algorithm recommends for you and which comments on highly commented threads will be at the top and being verified doesn't protect you from being blocked by me.
Or at least that was the way in the past, haven't used twitter since a long while.
And the main purpose is to filter out all the pointless noise which existence has in the end absolutely no meaning for you. Keeping some of the clever expertised subtle manipulator in your timeline can be useful to better understand what is going on. You know like the people which aren't just misguided or afraid but are instead misguiding and outright deeply rooted evil knowing exactly how much pain and suffering their manipulative spiel will create.