Preservation and sanitation is the primary reason why.
Although, back then, some people believed in the superstition of corpses rising from their coffins.
Actually, there was a fear of being mistakenly identified as deceased and being buried alive. For this reason, bells are sometimes attached to a coffin, so that when it’s rung, others are notified if the person in the coffin is actually alive.
Oh, on that matter, and in regards to U.S. law, note United States v. Causby, 328 U.S. 256 (1946)
It was a United States Supreme Court decision relating to the ownership of airspace above private property.
In regards to “ad enfernum,” which posits that property ownership extends “to the center of the Earth”:
In regards to to outer space, note the Outer Space Treaty (1967). According to this treaty, no nation may claim sovereignty of outer space or any celestial body.