1. It adds cost, weight (not just the pump, but requires more current and therefore a higher capacity charging system)
2. It increases the size of the tank, without necessarily increasing the capacity
3. A submerged fuel pump cannot use all the fuel in the tank, so that gives less range on the same quantity of fuel.
Fuel injection runs better cold and at altitude. However, the TK MV28 on a 2017 has a vacuum operated slide and needle which adjusts mid range mixture for altitude.
As for MPG, it would be difficult to better 78 MPG.
Carbs can be generally repaired roadside.
Yes, EFI is less effected by storing ethanol fuel too long, but I was delighted to have one last carbed bike.
Yamaha has developed a simpler EFI system for the XT250, etal:
On my Bonneville, not having to remember to turn on the petcock is an advantage and over 112 MPH out of 865cc is partially attributable to EFI.