How it was necessary to create weldment?

From the beginning SW had part file,assembly file and drawing file.Later (SW2004) we get possibility to have several bodies inside one file. But after this I think SW went wrong way:they made weldments which contains a lot of bugs up to now (SW2018):

I found out that PTC Creo use usual assembly for weldments.In this case it is not necessary to make cut-list, their cut-list properties,derived parts with transfer of cut-list properties to file properties and so on.

Assembly can provide all functionality weldment have.

So why SW made one more essence (weldment) which born a lot of problems and bugs?

SolidworksWeldments