Why Not Just Fire Everyone?

Compared with the private sector, career civil service is known for its job stability. From an internal, employee recruitment and retention perspective this makes government work appealing. On the other hand, from the outside (and sometimes from the inside) the fact that the system is set up for stability can make it seem like we don't manage poor performers appropriately.
The private sector version of what to do is efficient, but also extreme. (Donald Trump's famous line "You're Fired!"?) Is this what has to happen to improve performance in government?
Having worked in the private sector both for a large company and for a small business I think the answer is no. We should not just be able to "fire at will." Not because government workers deserve a form of welfare, but because it's poor leadership and management to dispose of people at whim.
Consider the parallel of family. When you start a family - whether it's marriage or partnership, or whether you have children or adopt them, or even when you are with a group of friends so much that they become your family - you don't just walk away when things get tough. That's what makes a family a family instead of just a group of random acquaintances. 
The effort that goes into building family relationships is not just a mushy nice thing to do. It's a socially and economically productive activity that promotes self-sufficiency, empowerment and responsibility. People from safe, stable families are able to work, raise children, and lead productive lives. They are less likely as a group to engage in violent crime, drug abuse, and other social problems that then become the responsibility of the larger family - e.g. society.
Similarly, work environments that promote stability facilitate a sense of safety and trust among employees. While nobody should ever get so comfortable that they slack off, if you're constantly looking over your shoulder in fear, you can't exactly be productive either.
In government and in the private sector, the key is to do the difficult work of recruitment upfront, then invest in keeping the new employee engaged over the long term. The higher you go in the organization the more time you should be spending on leading and managing people as opposed to carrying out technical work. In government, in practice that means that SESers, GS15s and even GS14s should be engaged deeply in relationship building and mentoring at the very least. This is a job that cannot be delegated or outsourced.
Once there is a sufficient level of trust and commitment in the organization, dealing with performance issues becomes less of an issue because nobody wants to stay in a job where they're not a good fit. When the organization is invested in the wellbeing of the employee they can help the poor performer better understand what's going on - and may even find out the issue is not organic to them at all: a bullying boss, a dysfunctional team culture, or perhaps it's illness or a family situation.
Either way, promoting a high-performance culture does not mean treating people like they're disposable. It's really about investing in managing them (us) like the assets they (we) are. That takes time, and caring, and skill. And no it's not "operational." But I'm willing to be you, dollars to donuts, that for every stubborn "operational" or "technical" problem there is a "people" problem lurking not so far beneath the surface. And once you understand what it is, you can chip away bit by bit at the corrosion and set the true productivity inherent in each individual free.
Like Freud said, health is the ability to love and to work. No matter where the workplace is, if we take care of our people then they (we) will take care of the work part.