Re: It's about government control
SpaceX's record on planning isn't very good. A long time ago their intention was to design a disposable booster that was so cheap to manufacture that it didn't matter that it was being thrown away every launch.
To this end they did do some quite clever things, including the original design of their rocket engine bells. These were made by forming two bells from sheet, pressing one of them to be crinkly, fitting one inside the other and welding / brazing them together. This made all the cooling channels for the bell in only a few operations; quick and a lot cheaper than brazing miles and miles of tubing into the shape of a bell.
Anyway, it turned out that they couldn't get the price down far enough that way. So disposability went, re-usability came in, hence their landing legs, etc.
This is called iteration. It's why SpaceX are running a lucrative launch business and SLS isn't operational. They ran with something, realised it was sub-optimal but worked, so tweaked the design in-service whilst moving forward in incremental blocks validating the rest of the design as they went - instead of allowing the entire project to stall. This contrasts favourable with SLS which has spent over a decade trying to develop the perfect booster to replace a system we already developed in the 1960s despite having the head start of reusing major components from the Shuttle.
Re-using Shuttle engine and solid booster designs is an excellent way to achieve this.
Ah yes, the Shuttle. Unique amongst operational launch vehicles for having no useful launch abort that could separate astronauts from the single most complex part of the launch stack (and consequently most likely to fail - which it did, once).
And when it comes to getting Falcon / Falcon Heavy man rated, meetings between NASA and SpaceX on this topic didn't go well; turns out you can't just claim it's reliable, you have to do all the paperwork to demonstrate that.
And yet despite this, NASA intend to put meatbags on top of SLS on it's second launch.
Meanwhile SpaceX has 49/51 successful F9 launches to it's name, and both the failures would have been survivable had they been carrying a Crew Dragon capsule with a launch abort mechanism.
I know which rocket I'd strap myself on to.