Maybe your car doesn't have a good fit. Maybe you have a truck cap and you want to rack it up. Who knows why, but you need a permanent mount. Okay, so it all seems...well...so permanent.
Quit yer whining and commit. You'll be glad you did. Many of us Cartopians have cars and trucks with special needs, so we're pros at committing to a rack relationship.
Thule understands this problem and provides a number of ways to take care of the permanent install. Okay, sometimes a drill is involved. However, if you a) have enough confidence, b) have a friend with enough confidence, or c) know someone who owns a body shop, it's not a problem other than a psychological one.