Why an atmosphere that only extends a few miles upwards? Why a radiation belt starting a thousand miles out?
Simple! God couldn’t trust man to leave a planet that man was bent on destroying! He wanted man to remain in place to reap what he sowed, here! Then, IF he learned from his mistakes PERHAPS he MIGHT be able to be trusted with the REST of Creation, the Universe! But he hasn’t proven himself able to yet, has he? ESPECIALLY the USA!
(And, while on the subject, Russia has ALWAYS been ahead of the USA! AND smarter!)