Comment by digital_voodoo

It's high fees, burdensome sanctions/AML checks (especially if the said country has been recently or is still on a GAFI list), plus the suboptimization of the core banking systems regarding international transfers, that make the whole things happen in weeks (or sometimes never happen if the end beneficiary doesn't start pinging, emailing or phoning its bank every now and then). The whole unreliability/unpredictability of the thing makes it undesirable for regular operations.