If they don't have world-execute permission, an access(2) check for executability would return negative, leading to things like shells not tab-completing it. The kernel would also deny attempting to execute it, as it is not executable for your fsuid.

  $ sudo chmod 4700 hello
  $ ./hello
  bash: ./hello: Permission denied

You need execute access in order to launch it, but in order for it to run, the user it is running as (not you) needs read access; you don't.