Radio towers are at much lower altitude, so you need way more of them than satellites to cover the whole planet. Also you need permission on land and you need a

Radio towers are at much lower altitude, so you need way more of them than satellites to cover the whole planet. Also you need permission on land and you need a boat in addition to the tower on the sea. Plus always having line of sight to the tower is harder unless you make them extra tall. I assume that makes them much more expensive and is why cell phone coverage is not global.