That is a limitation that is imposed by the FAA. Many airlines simply have decided that the risks do not out way the economics of doing circling approaches and thus have backed into the procedure by using basic VFR mins for such an approach, 1000' & 3 SM. The frequency of circling approaches in say a B777/747 and in some cases the B767 are so infrequent that unless the particular carrier has an airport on their list that sees this kind of activity, it's easier to just skip it, The Circling approach takes up a lot of sim time that could be used in another disciplines. I just did a requal in the B777 and the Circling approaches while kind of fun, ate up a copious amount of sim time in the process.