Reason sab technical hi hai. Bhale hi Loco naya ho each and every part of the engine, s/w, microprocessors, traction motors, etc. CLW SE ENGINE bahar aaya uska zyada trial run shayad hi ho pata hai use direct Loco shed ko allot kar dete hai. Then ye sab kaam concerned loco shed walo ka hota hai. Passengers ke saath isliye kyuki agar engine me kuch malfunction hi bhi jaaye passengers kaunsa time pe chalti hai kahi bhi. They have to halt at all stations. Direct m/e ke saath daudana thora risky rehta hai. Would request some senior technical iri member to throw more light on it