For Trinitarians, why is it important to posit Jesus's human nature continued existence post ascension?

Christians belief that God exists in three persons, although being just one entity. One of them is the Father who created the visible and the invisible world. I understand, that the Father was just active in the beginning. He does not interact with the world as of now. (Maybe he's doing something people can not explain. But maybe this is done by the Holy Spirit - the third in the club...) The Holy Spirit is another person. This is all the good thoughts. This is still active in the world in many people. This is how God interacts with people. And there is/was Jesus. Jesus was both fully human and fully god. He was crucified but was resurrected after three days and some time later ascended to heavens. As God is also in heaven, the question is if there is any need for the son as separate person anymore. Or has this person rather united with the father, as the need to also be fully human is not there anymore, as Jesus is not on earth? To be more precise: What evidence is there that Jesus is still a separate person, even after his ascension? What are the reasons Christians believe that?