Very true, something that Star Trek completely overlooks, because it's not expeditious for the stories. Anytime you travel such great distances, time moves much more slowly for you relative to people on Earth. When Picard made it back to Earth to visit his relatives after the Borg incident, his brother Robert would have been long dead! In truth, when Voyager returned home they would have been greeted by the great grand children of all the people they had known.
In Trek when warp drive is used the crew never encounters time dilation I guess because of how the fictional technology works, they never fly at relativistic speeds so time doesn't go slower for the crew compared to someone still on earth.