Short answer: profitability and purchase price
Long answer: If I sell super sturdy tents, you'll only buy one in your lifetime. If I sell tents that fail faster, chances are you'll buy several over time, hence my revenue stream is likely to be healthier.
Now I could just charge a lot more for the sturdy tent to offset that, but then fewer people will buy them because initial purchase price is most important to many buyers. The demand is for lower prices. How to satisfy that? I use cheaper materials to drive the manufacturing cost down so I can sell them at a lower price. The downside of that is that they don't last so long, the good news is I can sell more of them.
So I can choose to sell a few expensive durable tents or a lot of cheap flimsy tents. Since 2008 the trend is towards the latter.