Those who have passed away often describe finding themselves outside of their dead bodies immediately after passing. They don't realize they have died, and may walk around the scene as though they were still in a body. Passing into spirit doesn't result in a sudden transformation. After they die, they are the same person they were before death, just without a body.
When the person dies suddenly, there is no time for a preparation or transition. The person is in a body one instant and out of the body the next. They don't know what has happened and must come to a realization over time, often with the help of a guide. Loved ones will not be there to greet them because they didn't realize their passing was imminent and weren't prepared to be there.
As a result, those who die suddenly may linger around the places they frequented while alive for days or weeks, able to see everyone and perform such routine activities as getting on and off of busses, but they are not able to communicate. That is illustrated in Ted Butler's account of his passing.
Others described being greeted by a loved one. That is especially true when the person has been dying for a period of time and the loved ones are prepared for the transition. It is common for the dying person to begin the transition into the spiritual realm even before death through visitations from or dreams of deceased loved ones. Elisabeth Kubler-Ross suggests that children, especially, actually begin to make trips to the spirit realm in preparation for their passing.
Leslie Flint's seances include an account by a man named George Wilmot of being greeted by a loved one on passing away.