I am very much in-favour of this idea, of not launching SLS (Space Launch System) on it's maiden flight as a crewed one. Exploration Mission 1 (EM-1) has plenty of objectives that will be carried out and does not require a crew.
There are those who laugh and think that it's a snub at President Trump. No. His administration asked if it was possible to make it crewed and accepted NASA's judgement. This EM-1 mission has been considered on and off at times in the Obama administration as a possible crewed one as well.
Though cost may be the main cited issue, it's also about safety and the timing and training of the assigned crew in time. SLS, and the Orion capsule are still facing delays even with an aggressive program to try and meet a 2020 deadline, or even 2023.
The Europeans, through Airbus are part of the problem with delays and trying to make the Service Module work as designed. Honestly it feels like anything Airbus touches that is not an airliner goes to hell with delays, cost jumps and technical issues, so no surprise that Lockheed Martin - the capsule maker is only part of the delay.
Even if Orion and SLS were fully ready for launch by 2018, it would be a bad idea to send the first all-up launch crewed. Why risk human lives on still prototypical systems?
The Space Shuttle launched for the first time on April 12, 1981 with John Young and Robert Crippen because the Shuttle was not then equipped for fully remote flight control, as would be possible in the event of an emergency in the wake of the loss of Columbia in early 2003.
Besides the Shuttle, all other programs - Mercury, Gemini and Apollo launched with unmanned capsules atop of properly instrumented test rockets - the Redstone/Atlas D, Titan II and Saturn V respectively.
Do not rush human spaceflight, especially when the problems will take many months to come up with a fix or solution, and to test it, validate it and implement the changes.
In 1967, the Block I Apollo 1 capsule with Gus Grissom, Roger Chaffee and Ed White was engulfed in flames, and the three astronauts suffocated within the sealed capsule during a launched rehearsal test.
Why? Because everything had been rushed. The design was flawed, quality control was sub-par with exposed wiring and a hatch that took over a minute to open. The astronauts suits, and the capsule's material was full of flammable material such as nylon, which burned, melted and gave off overwhelming toxic fumes. And this is what was termed - Go fever.
The urgency to meet a deadline, North American Aviation dropped the ball on the design and construction and QA. NASA did not do exhaustive check-outs of the arriving capsules, and the urgency to meet President Kennedy's challenge of reaching the Moon by 1969 was such that even raising concerns of safety issues could land one in hot water with NASA administration.
The same could befall SLS and Orion if a crewed launch was shoehorned in before it is all ready. It's a phenomenal system, and while yes, it is the creation of the US Senate in many ways - SLS is also going to be the most powerful rocket ever built by a fair margin.
And if we are to go to the Moon, Mars and beyond, the incredible power and flexibility of SLS is what will be needed to heft such weights to vast distances in deep space.
Rant over... I think you figured out who typed this... :)