because it seems to them like the musicians are becoming equal to them,and preparing against their will a future rivalry
they fear that those europe trip on their own will end up in "he started recording secretly an album"
i think the musician who travelled the most on his own is by far was heritier but it was creating its fair share of problems for him just that he'd dominate it through his jesters doing dirty missions at times and due to his son and mother brother and sisters relationship with the ngiama women
i remember a story back in the days of koffi being furious when he found out that titina was taking the same trip as him to europe when they were given a time off between african tours and tricking him with the ticket,forcing titina to activate last minute calls to donors to get another one
or how it would take months and years at times for abraham to be allowed to go to europe because of the gossip that he was preparing a rebel group which would bounce as soon as his heavily funded solo album by jb is released