Because they are nothing but lazy. SR especially MS/MAS div base has lost many prestigious train cause they do not want to handle it anymore mentioning they are saturated and will make a way for new trains. Some examples include MAS bangalore mail, mumbai mail, Howrah mail, mumbai express, TVC mail (now in cbe base), Cape express (used to MS base now and then made as SWR train and then TN base and now back to SWR). Boat mail, Ananthapuri gone out of MS base. God knows what I missed in this list. All these are good trains MAS/MS gave up to other base/zones.