I can't say for sure but in my own experience every tank I've had with plants in has had these, I've also read that if a tank
doesn't have copepods then something must be seriously wrong (the website I linked you to mentioned that). They're a natural part of an aquatic ecosystem and I imagine they do have some level of benefit, even if it is just as extra protein.
I am of the opinion that quarantining your plants will reduce the numbers that are introduced into the tank but in time they may show up anyway.