What causes laptops to break in the long run?

It's the great increase of technology. Back in the 'good old days' of 80's and 90's, when you bought a very good laptop, you were spending thousands of dollars. $5,000 for a laptop even up into the 90's was normal! But you were sure of a great laptop.
Back then, pride DID mean quality.

But as the average technology of chips advanced every 18 months, so did the hardware and software to accompany it.
Now… In 2014, the difference between a $400 laptop and a $1500 laptop is very little concerning quantity of the hardware.
If a laptop is $400, then add couple hundred, and you upgrade to one terabyte hard drive. The high end laptop will have some better components, but not as drastically better than the lower cost model. Perhaps much faster chip, better cooling, mega-hard drive, small changes like that.

But now, many laptops sold are pretty cheaply made, so they can be sold cheaply. I know for fact that HP makes and sends damaged laptops from its factory, several models have design flaws of hardware or software issues, and they get sold at stores that way. Then HP will let everyone spend hours on a customer service line, with little success to show for it.
Other brands may not be much better, but I think HP is the current evil right now.

So overall, it's the improvement in technology that has advanced so much in past decades, that the difference between a cheap laptop and a good laptop isn't very much anymore. And you know, that if they build something cheaply, then they make more money for the factory and company. And cheaply made stuff means cheaply made parts.

For hardware, if the display breaks you're basically screwed. Unless you want to pay a lot for it to be fixed! Also, any water damage will break the laptop almost immediately.

My power cord connector ( in the machine) broke or bent or something. So i needed NOT a new power cord, but a new machine.