Apple has nailed the human sense that everything is forever
iCloud to back up everything; your iMessages, photos, videos, contacts etc etc etc.
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Stability that very rarely falls over no matter how many Apple devices you are using.
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The lock-in of Apple Pay, iMessages, Apple News+, Arcade, Apple Health etc etc.
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Long term familiarity, satisfaction and loyalty.
How many times does Google drop services with relatively short lead times and how many startups, and even more stable brands, fall over unexpectedly? It is common enough to make me feel uneasy about relying on non-Apple brands and it is not just because on a fanboy-ism for the company.
Think about the tools and apps you have used for a long time and how many Apple have dropped. I cannot think of any at this point and as such I have years and years of messages, thousands and thousands of photos, and a digital history in the palm of my hand, on my wrist, on a tablet or a laptop that will grow with me.
Crucially, I do not have to administer my history and do not have to spend hours backing everything up because it is done every day for me. It is logical to keep a completely separate copy of important data such as photos, which I do, but even then it is a rare activity and such minimal effort is required that I barely notice it.
This has not happened overnight and I doubt that luck is a big factor in this. There may have been changes of direction along the way, but if there was a plan a decade and a half ago to integrate everything and 'stick' people to the Apple system it has worked incredibly well.
Most people do not want to think about tech and they do not want to waste time managing digital information. They just want to live their lives and use technology to enhance their experiences. It appears that Apple understands the place people want their technology to be better than most.