Yes I know all stations do not have EMU.
Logic behind EMU ticket to enter on platform:
If one has to enter on platform & if platform tickets are not available...
then only legal way to enter on platform is purchase journey ticket.
So...
more... it is beneficial to purchase the cheapest journey ticket to save the money.
The ordinary (EMU/DMU/Passenger) ticket for nearest station is cheapest ticket available on that station.
(In Central Railway, minimum EMU ticket is 5Rs. whereas platform ticket is 10 Rs....! so many people purchase EMU ticket & enter on platform to save 5 Rs.)
One can purchase EMU ticket on stations like NDLS, NZM.
.
One can purchase DMU/Passenger train ticket if EMU not available at that station.
If no EMU/DMU/Passenger train from that station....then
One can purchase Exp. train ticket of nearest station (where train halts)....to enter on platform.