Ty decided to interfere a little bit for Tylie's sake. It was a little bit at first like negating some of the force she felt from the friction and air of Earth... and then some strengthening of her body... and then some modifications to her body... and then some modification to the bodies of others. By the end of her life Ty's subconscious was doing so much for Tylie that Ty just sighed and let June and Mark into heaven as they weren't necessary.
Ty tried a few other times to get children or people of heaven onto earth, but always came to similar issues. He tried not letting people from heaven go to Earth anymore, but then the people of Earth started getting anxious that the world was turning to hell or something. Ty deciding to spend more time focusing on Heaven and perfecting it that he'd just let people go to Earth with some of his subconscious to grant their wishes. A lot of people in Heaven also stopped looking at what was going on in Earth and just enjoying themselves and their growing families in Heaven.
On Earth the Heaven people who were still interested had basically took ownership of areas of "Earth". While everyone stilled called the place before you went to Heaven Earth it was less Earth and more the entire Universe which kept expanding and more Heavenly people were able to claim and develop their own Earthly worlds on. There were Heavenly people who created unique worlds, Eden worlds, "Earth but with something different" worlds, etc. Some wholesome others depraved, but the most important was Earth the original. Joe's family claimed ownership as one of the first heavenly families along with Dustin, June, and Mark. They rarely went and mostly let Earth expand a little to keep up with population increases and replenished resources, but they made sure to keep it isolated away from all the other heavenly families and their worlds. Once the people on Earth died and were curious about the rest of the universe then they would at least be safe from some of those people...