The purpose of it would be passing parameters to the executable when DOSBox is started as "dosbox filename" where filename is an executable.
For the average user this could be handy when making shortcuts for the game, e.g. using "/nointro" parameter.
Personally I'm requesting it because I'm working on project Coopnet, and we decided to add support for DOS games by using DOSBox. The lack of this feature is quite a problem for us. The workaround for this would be messy.
Adding this shouldn't take long so I hope you will add this in the next release.