Why does the train from Brussels to Prague stop in Den Haag HS and Amersfoort, but not on the return journey from Prague to Brussels?

On the Prague - Brussels service, these stops don't fit the timetable due to heavy rail usage. Travel to Amersfoort or Den Haag HS from Amsterdam Centraal or Rotterdam Centraal stations. From Brussels to Prague, we do stop in Den Haag HS and Amersfoort.