In the US at least we put all our eggs in one basket (the Shuttle) and ended up foregoing about 2 decades of development in conventional launch vehicles (until the Challenger accident forced some sanity). Also, a lot of the big aerospace companies (such as Boeing) have surprisingly shallow experience with orbital rocketry (although it's improved a bit with the EELV generation). Very few folks at those companies actually had hands on experience with building or flying rockets, and even less experience with testing (as a rule most launch vehicles fly straight down the middle of the flight envelope as much as possible, so even in a vehicle like the Shuttle with 130+ flights that's nowhere comparable to having the same level of understanding or confidence in the vehicle if it had flown that many flights while exploring the envelope).

When government does something, it tends to put all its eggs in one basket.

And the way lobbyists run our government makes the problem even worse, as there's more pressure to keep spending regardless of results.