That's the thing, some companies want the materials that the ships bring back, and some would prefer to sell them. If everyone in the company has access to the ships, then the ventures would be canceled, company credits would get wasted, and some players would simply destroy the ship either accidentally or just because they can. I know in my company the leaders have been the only people contributing to the building of things, and therefore no one but the top four ranks have access. The materials that are brought back are only for more company crafting stuff, maybe some low grade materia. There's really nothing to "play with" at this point.