ORIGINAL: robberthooij
[edit: I need to learn to read, it are not the labs but the plants i'm talking about -> so effectively changing my question into: do i need these plants?)
Plants are needed to turn the raw materials (ex:steel, polymer, etc) into the components of your ships (ex: guns, engines, cargo bays). Space ports and construction ships require them to do their job - and so are mandatory.
That's the "why" to your question.
