Thanks,

I was using the Swedish CAA flight plan submission system which sends IFR flight plans straight to the IFPS. VFR flight plans are sent to a briefing officer for manual checking and they can fix obvious errors such as omitting DCT. (Although one time when I submitted two VFR flight plans in succession with the same obvious error, they corrected the first one silently but called me to complain about the second one.)

An IFR route would normally be a list of significant points separated by ATS route designators, the DCT is use to replace the route designator where there is none (as in a VFR flight) this makes parsing easier.