I’ll answer this question from the perspective of the difference between a long hike and a weekend hike. And that difference is:
Something will go wrong.
Going wrong can take many forms – you can get lost, hurt, etc. But the most common forms of adversity on long hikes are gear failures and bad weather.
If you are just out for the weekend, it’s not likely that any decent quality gear will have time to fail. And if the weather is bad, you can just stay home or turn back. If you are out for weeks or months, though, these low-likelihood events become highly probable.
Here are some examples of gear failures I’ve encountered over the decades: cracked housings on water filters; cracked O-rings on gas stoves; a bear puncturing an aluminum fuel bottle; leaking sleeping pads; waterproof-breathable jackets that are neither; water bladder seam splits; zipper failures too numerous to count.
I have steadily replaced failure-prone items with simpler and usually less expensive gear. I avoid anything with a pump, a valve, a seal, a switch or a zipper.
I replaced white gas stoves with an alcohol stove setup that can also use twigs when I run out of fuel.
I replaced inflatable pads with a foam pad.
I replaced water filters with chlorine dioxide drops
I went back to using a poncho – which is both truly waterproof and well-ventilated – after top-of-the-line WPB jackets left me soaked in all-day storms. Gore-Tex lined shoes also fail in these conditions. I wear well-ventilated shoes and bring 3 pairs of socks so that one pair is always dry in the morning.
On desert hikes I bring several small water bladders and bottles so that the failure of one is no catastrophe.
Note that most of these replacements not only make my gear kit more robust, but less expensive and less heavy as well. This is bad news for the recreational industrial complex, but good news for your finances and your knees.