The side cores for this flight are reused Falcon 9 first stages, while the center core is new. Falcon Heavy center cores are structurally reinforced, and hence are different enough from Falcon 9 that you can't reuse one as the other; whereas converting between Falcon 9 first stage and Falcon Heavy side booster just involves moving around some external hardware.
The government has done good work on this issue - it's bootstrapped a market for launches using its purchasing power in military launches and ISS resupply contracts, while actively working to preserve a competitive environment and avoid monopolies. It also provides essential services like range safety and airspace management; what's getting in SpaceX's way is the lack of government.
Citation needed, especially as I'll just note we're using a website, many innovative technical elements of which were government funded.
Here's an opinion piece from WaPo this morning on the subject: https://www.washingtonpost.com/opinions/dont-buy-the-spin-go...
tl;dr: Shutting down the government gives credence to those who base part of their political programme on "government is evil lol", when really they just want less regulation on behalf of wealthy donors -- a fundamentally corrupt bargain.
If SpaceX had built their own launch facilities instead of using the government’s, they wouldn’t be beholden to the shutdown like this.
They have in the past.
https://latechnews.org/spacex-launches-bulgariasat-1-recycle...
Government is normally getting in the way or at least slowing down the process of innovation. Hopefully that doesn't happen here at to much a cost to SpaceX and the U.S. tax payers.