Which runway to install an ILS on can be influenced by a number of factors such as average wind, noise sensitive area and protection of the signal out to the specified angles and distances. The missed approach procedure may be a factor as well, At some airports, such as Phuket, the localiser can't be lined up with the runway because it ends in the sea and is situated at the side of the runway before the end instead. A slightly offset approach with a higher minima is required, 1.4' offset with a D/H 458 feet agl for CAT C aircraft rather than a typical 200 feet agl D/H.
In Cairns, the ILS often goes out during a cyclone due to it going underwater.
Like most things in aviation, it's a compromise.