Why international hotel chains reject candidates who does not have knowledge of just opera PMS since they have experience with other PMS ?

Most of international hotel, are using Opera PMS, and not other PMS however this does not mean to reject a candidate for only that reason.

because most of international hotel chains they are using micros opera system even the local chains they start to configuration opera system its very secure and easy to access PMS etc.therefore most of candidate if they don't know how to use the micros opera the clients reject the candidate