In short, when it comes to X-vehicles, NASA just doesn't get it. A couple years ago, some space activists began to argue that X-vehicles no longer mattered. Unfortunately, the commercial RLV companies have run into investment roadblocks in the past two years. Investors lack confidence in RLV companies for several reasons. Current launch markets are small compared to the required investment.
New markets are speculative and uncertain.
Technical risk is high compared to most investments, and space technology is outside the experience base and comfort zone of most investors, so the perceived risk is even higher. Private industry must pay attention to the bottom line. There is no way it can fund purely experimental vehicles that carry no payload and serve no commercial market.