Typically this implies that there is some fundamental issue (or, more likely, several of them) causing these problems. Since nobody really knows what the real cause is, we are free to wildly speculate and hypothesize that the problem lies somewhere in the human brain. Not any single person's brain, mind you, but fundamental properties of the brain itself.
What the brain does incredibly well
The human brain is an incredible piece of work. Millions of years of evolution has adapted it to be able to be able to do astonishing things in the blink of an eye. The fact that you can walk and talk at the same time without needing to use any conscious effort on it is nothing short of amazing. As a concrete example, look at the following picture for a couple of seconds and then continue reading.Just a quick glimpse should give you a fairly good idea about the quality of these two very different vehicles. These include things like top speed, acceleration, insurance costs, ride comfort, perceived increase in sex appeal, fuel consumption, maintenance effort, reliability, how long they are expected to keep working and so on. The estimates you get are probably not 100% accurate, but altogether they are probably mostly correct. Given your current life situation you probably also immediately "know" which one of these two would be better for you or that neither is suitable and that you need something completely different, such as a van or a bicycle.
This is your brain doing the thing it does best: examining physical objects in the real world. This works because things that are made of atoms have noticeable and persistent properties. These include things like mass, durability, sharpness and so on. This consistency allows one to fairly accurately estimate their behaviour even in unexpected situations.
And where it stumbles
If you ever find yourself bored at a party, try the following. Find some people, explain the Monty Hall Problem to them and give the correct answer. Then spend the rest of the evening watching how people will argue until they are blue in the face that you are wrong and that the probability is 50/50 and changing the door is not beneficial. This will happen even if (and especially when) participants have higher education degrees in STEM fields.
The Monty Hall Problem is a great example of the deficiencies of our brain. The actual problem is simple but the solution is so counter-intuitive that many people will refuse to accept it and will instead spend massive amounts of time and energy to disprove the point (in vain) because it just "does not feel right". In mathematics this happens fairly often. The reason this is relevant to the discussion at hand is that, at the end, that is what all software really is: applied mathematics. It does not obey the rules of the physical world and atoms, it only exists in the realm of logic. Computers don't deal with atoms, only electrons[1]. To see how this translates to coding, let's do a thought experiment.
Suppose your job is to paint a wall. After a hard day of painting you have ten meters of freshly painted wall. The next day you get to work and continue painting. At the end of the day you look at your work: exactly ten meters wall covered in paint. Puzzled you check everything but can't find anything wrong. You should have 20 meters of painted wall but don't. The next day the same thing happens again. This makes your manager unhappy so he appoints three people to help. The next day the four of you start painting, working as hard and as effectively as you possibly can. When the day comes to an end, you have seven meters of painted wall. Somehow three meters of paint you had already spplied have disappeared and nobody can explain why or even where the paint went. Determined to make up for the loss everyone works extra hard and at the end of the day, finally, nine meters of the wall is properly covered in paint. Everyone goes home exhausted but happy to have finally made progress. The next morning it is discovered that both the paint and the wall it was applied to have disappeared.
Finally, software
This is the essence of creating software. Since it exists purely in the realm of logic and mathematics, you can't really see it, smell it, touch it or feel it. It has failure modes unfathomable with physical processes and these problems occur fairly regularly. This means that all the builtin functionality of your brain is useless in evaluating the outcome and quality of a software project. Code can only experienced through thinking, which is slow, difficult and error prone. As opposed to cars, comparing two different code bases for quality and suitability is a big undertaking. But it gets worse.
The output of code, like the web browser you are using to read this blog post, look and feel a lot like physical objects made of atoms. This means that when people who have no personal experience in programming either buy or manage software projects, they are going to do it as if they were dealing with physical real world objects. That is what they are trained to do and have years of experience in after all. It is also actively harmful, because software is electrons and, as such, beyond the immediate instictive grasp of the human brain. It does not play by the rules of atoms and trying to make it do so will only lead to failure.
[1] For the physicists among you, yes, technically this should be electric fields, not electrons. This is an artistic decision to make the headline more clickbaity.