It's really about the surface, which would be quickly destroyed by jet exhaust. One of the impulses for changing surfacing methods for runways in Soviet Union

It's really about the surface, which would be quickly destroyed by jet exhaust. One of the impulses for changing surfacing methods for runways in Soviet Union was early jets ripping asphalt off the surface, for example, though later planes had higher-mounted exhausts that caused less problems. As for road landing in Ukraine (and other Warsaw Pact countries, and Sweden), it's a mix of special road segments and special aircraft design (for example, consider MiG-29 with its intake shields that close when it's on the ground, and sturdier landing gear on many aircraft)