- Since the same technology can be used to make ICBMs, technology sharing has been slim.
- Budget priority is low. NASA operates on eighteen billion dollars, the ESA on three billion euros, the Chinese space agency something like 20 billion yuan, and the RKA even lower, around 35 billion rubles. Increase the budget by 1-2 orders of magnitude and we get a lot more flights - maybe not a huge number immediately, but a lot more after a few years of development.
- Political considerations.
Start spending ten or more times as much on space, and the infrastructure will be developing as quickly as you can to develop your nuclear gunboats. Hopefully by the time that you're ready to start building, launching, and testing them, you'll have managed to get the world working together, but it is a pretty tall order, and there is a slight risk of touching off a really deadly war.
Personally, I'd suggest preparing to surrender really well, preparing some good hidey-holes, and sending an ark should be as high a priority. Given unknown levels of technology and unknown numbers, there's the possibility that human tail is going to get kicked but hard at the least sign of resistance.
In some circumstances, swallowing our collective pride and hailing our new overlords for a few generations may turn out to be the best strategic choice.