Because NASA, with nearly 30 billion in funding and using technology designed half a century ago, took 11 years to build a Shuttle cosplaying as a Saturn V. They were legally mandated to. That's not a dig at NASA, it's a dig at the morons who hold their purse strings.
In roughly the same timeframe, SpaceX developed two brand new engines, both of which have amazing performance in their weight class. They developed a reusable medium lift rocket that's now one of the most reliable launch vehicles ever. Now they're working on a fully reusable super heavy launcher that's capable of interplanetary missions. And they did all that without NASA's budget.
Private launch companies, of which SpaceX is only one, allow for faster development, faster innovation and cheaper launches. They're actually saving taxpayers money. And the amounts that NASA does pay them don't just vanish into the CEOs' pockets the moment the payment clears. It goes to engineers, maintenance workers, construction workers, caterers, everyone employed by these companies and their suppliers.