Folding phones from 2011 to present: big screen, lack of apps, and why did Apple jump in?

This year, folding phones are attracting strong attention. Not only Samsung, Huawei, and Google continue to improve, but also because of rumors that Apple is about to launch a new folding model: a shorter device, nearly square in shape. It may not look as beautiful as the traditional long and thin iPhone, but it solves the problem that Android folding devices have been struggling with for nearly 7 years.
When did the folding phone story begin?
The idea of folding the screen is not new. Since 2011, Nokia has displayed concept models in London. By 2018–2019, Samsung and Huawei began commercial sales. Huawei came out earlier, Samsung initially had durability problems but then did its best with the Galaxy Z Fold series. Many other companies such as Google, Oppo, Xiaomi... also jumped in. The folding machine from an exhibition item becomes a real product on the shelf.

The Nokia model with a curved screen was demonstrated by Nokia at Nokia World London 2011. At that time, I didn't have a pocket so I couldn't record videos, only photos.
What is the real value of a folding machine?

The biggest limitation of folding phones is that there is no app
When opened, the book-style folding device has a nearly square screen (ratio of about 4:3). Meanwhile, over the past 10 years, regular phones have become increasingly long and narrow. Most applications are designed for vertical screens, so when used on folding devices they are often stretched, ugly or not optimal. This is the biggest weakness of Android folding devices, even bigger than the screen fold. Hardware has improved a lot: thinner, lighter, more durable. But the app still hasn't caught up.

People don't really need flip phones
Regular phones now do everything well: calling, texting, surfing the web, watching videos, taking photos... Folding phones bring the excitement of having a big screen, but most users don't really need it. It's like a cool piece of technology, not a must-have.
For what reason does Apple step in now?
Apple is not late. They wait until the most profitable moment.
Apple's biggest advantage is the iPad's app store
The Apple folding device is expected to have nearly square proportions when opened, similar to the iPad mini. That means they have tens of thousands of iPad apps already optimized for the big screen. While Android has to beg programmers to rewrite the app. Even though Samsung and Huawei make better devices, they cannot copy the iPad app store. This is Apple's "inimitable" advantage.

Total number of applications on the App Store (iPhone + iPad + other devices): About 1.9 - 2.4 million (depending on statistical source). Of these, 63.5% support iPad → equivalent to about 1,222,000 apps.