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).