Because we have no idea whether their souls have returned to the higher levels of the fourth dimension or whether a rouge spirit is masquerading as one of our loved ones.
Secondly in the spirit world there is no concept of family as we know it. We have all had many lifetimes within many races and cultures and of course many families so which family do you belong to???
The answer is simple. You back to the group on the level you are at. As in schools we have classes. At the end of the year we sit our exams and if we pass we move up a grade irrespective of your race. It is the same in the fourth dimension. As above so below. Race does not exist there either.
However unlike the earthplane if you haven't learnt your lesson in this lifetime you don't pass but come back again and maybe again to have another go. That is the purpose of reincarnation. To learn your lesson, purge all your past karma and move up a level. Eventually to get back to being at one with our Creator God.
On the other side of the coin, If they have not returned to the fourth dimension it means they are lost and still in the earth’s sphere and are under the control of the evil Lucifer and his Servants Molech and Baal. The evil ones will use them to sway you to follow in their footsteps and prevent you from returning to your group in the fourth dimension when you die.
If you smell, hear, see, feel, or have any inkling that a spirit is around you, your best course of action is to challenge them mentally to leave and pray for the redemption of their soul in eternity.
Sadly the majority of people today do not do this.