Startups are quick to hire and fire because hiring exactly the right person is important, and hiring the wrong person can cripple the company. Everyone who applies for a position at a startup knows how this works, and I'd argue that if you aren't okay with this atmosphere, you need to avoid the startup scene and go work for a big company with some decent HR policies.
The bullshit shows up when a startup succeeds, and the company tries to preserve its startup culture because they want to keep growing like a startup. You then get BigCo politics with startup arbitrariness, and that's a recipe for disaster. Similarly, sometimes the Good Idea Fairy whispers in the ear of a high-up executive, and he tries to institute startup attitudes toward hiring and firing at a BigCo. This also goes poorly.
For example, a civil engineer would need to have a degree in their field and then pass a series of stringent examinations to get an FE and finally a PE. Most will require a PE to practice their trade.
In tech an "engineer" may or may not have a degree and there may be certifications, but very few that I know of have ever provided any value. In my experience, there's also not as strong a correlation between a degree in CS for example and one's ability to produce software.
Lots of folks in tech come out of Enterprise IT where projects usually fail and the modus operandi is to purchase technology from vendors and blame them when it doesn't work out.
Or something like that anyway.
The other big group of fail that I’d point to is bootcamp developers.
In general, Americans see this protection as none of the government's business. If the business wants to provide it, or unions want to demand it, that's fine, but it's not going to be applied as a blanket policy.
Many businesses do apply some sort of lengthy process for firing people, for the simple reason that experienced talent is valuable and removing it capriciously is a terrible idea, but it's not required.
In my experience, however, even these processes are just drawn-out kabuki dances. By the time that you've been formally notified that your performance is deficient, the decision has already been made to fire you and nothing will change their minds.
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As for whether this attitude is a good idea, I'm mixed. On the one hand, it allows businesses to take a risk and hire inexperienced or otherwise dubious prospects without fear that they'll be stuck paying a useless body for months after it's been found that they're a bad fit. On the other hand, it allows shitty managers to be thundering assholes and capriciously fuck with people's livelihoods.
However, I'd assert that the American attitude toward employment is critical to startups. A BigCo can be indifferent to keeping a shitty employee around for months. A startup has much, much less margin for error.
1: https://en.wikipedia.org/wiki/The_Protestant_Ethic_and_the_S...
So both sides benefit, the company has the initial flexibility to hire and fire and after that the employee gains some assurance that he won't be thrown off the premises arbitrarily.
When I started most UK tech, and companies in all other industries had an initial one month probation. Very occasionally, usually for the most senior roles, it might be two or three. Six months weighs the balance much too heavily on the employer side I think.