In a commercial application they need to be used since that what is specified in the design but in reality making an equivalent capacitor out of many smaller value ones would do the same job for far less cost. Or just find who makes them and buy ones that are not Miller branded or packaged.
When I worked on those machines every day and thusly ordered overhaul parts buy the case work to keep up with them for warranty alone I figured out who made their parts and components like their 300 amp 1200 volt IGBT blocks that they retailed for ~$600 a piece were just rebadged common brand name units that sold for $100 - $150 tops without the Miller stamp on their side.