It's because flagship spacecraft and things like the LHC are projects that require a budget of several billions and a 25-year commitment. This kind of budget is within reach only of a wealthy nation with stable finances and a stable political system.

I think the budget explanation also explains the pharmco crisis. It takes about a billion and a decade to bring a drug to market, and that's why you see statins, antidepressants and antidiabetics in the pipeline. Meanwhile, antibiotic resistances are going to be a public health crisis, and Chagas disease, sleeping sickness and malaria are major killers in the developing world. A new model is needed here; we don't need to try coroprate sponsorship in space when it's already failing on Earth.