There are many reasons, but here are some of the most important:
"It just works" (concerning built-in apps) - I think AirDrop works amazingly, it is as easy as asking "Do you have an iPhone" and then you are 99% sure you can just drop over photos without any problem. It seldom lags for me. If I have a Huawei, let's say, I can use Huaweis similar service called "Huawei share". The problem is that it isn't as consistent, and even if the other person happens to have a Huawei (which isn't that common here), it isn't a guarantee that it does work. The camera app works great every time you pull out your phone from your pocket. You can simply drag-and-drop the subject of any photo which just works. The built-in mail apps sync very well with lots of mail servers etc. (I have not found any good todo-list app for Android that syncs with my Outlook/Exchange todo-list, even after lots of searching).
"It just works" (concerning third-party apps) - stuff just works. On Android, you find that some apps just works on certain display sizes, some apps just look really bad on some devices, some apps take bad photos on some devices, but that isn't a concern on iPhone. I have not had any apps display poorly that only displays well on some other models.
Design of apps - the design of the built-in apps are cohesive and works amazingly together. You know how each app should "feel" like, how the search bar should "feel" like, in any app. For Android, my experience has been a lot different. Of many built-in apps, some are from Google and some are from the phone manufacturer. They might be completely different in design, feel very different, and sometimes built-in apps are even competing with the manufacturers' apps (Google Play Store vs Galaxy Store, Google Chrome vs Galaxy Browser etc). I haven't had a very extensive recent experience with Android, but I felt like third-party apps on Android had a lower chance of using the system look and feel compared to on iOS. Also, many beautifully designed apps are available only on the iPhone, or become available on the iPhone first, and I appreciate good design.
Seamlessness of ecosystem - it is so easy for me to just copy a photo on my iPhone and paste it on my MacBook. It has worked 100% flawlessly every time. If I am out of WiFi range, my computer knows that it can use Bluetooth to activate Personal Hotspot on my iPhone, I don't even have to take it out of my pocket. When I am in a work setting, I can press the do not disturb button on my keyboard, and my phone stops vibrating. I can pick up a call on the computer (which I do A LOT), and even move from computer to phone and back. I can share tabs on Safari between my phone and computer, I can send SMS and iMessage from my computer, etc.
Better performance - it should come to no surprise to anyone that the performance on iPhone is just superior. This isn't just due to the processor clock speed being higher, or that the chip is made with a more advanced chip manufacturing process (all of which contributes to its low power usage), it is also due to the software being more optimised. iOS have a lot lower overhead than Android has, which makes it faster by default. It has better memory management, which is the reason that iPhones have survived so long with so little RAM available. Additionally, since there are a lot fewer iPhone chips, it is much easier for developers to optimise apps and to take advantage of the Neural Engine, for example. Apples API's (the way app developers tell the iPhone chip what to do) are made to make it as easy as possible to use such features when they exist. Contrary, on the Android side, many different chips and many different implementations of similar but not the same additional features (such as the Neural Engine or dedicated image processing pipelines) generally don't have the same API and that leads to extra job from the developers to take advantage of them. Therefore, many developers don't use them, and Android performance drops.
Design - I really like the iPhone design, it looks stunning. I currently have an iPhone 11 Pro Max and will be upgrading to an 15 Pro Max, both of which looks amazing. Sure, there are nice phones from other manufacturers, but if I would go looking for Android phones, 3/4 would be a big no-no right by the design.
Longevity - Apple is well-known for supporting their phones for many years, both with iOS upgrades and by making repairs available. I still have my iPhone 11 Pro Max up and running after 4 years. It works just fine still, and I am mostly upgrading because I want a better camera. The battery has gotten a bit worse (as batteries do), but I am certain that it is easier to find a battery replacement for my phone on the street than for the majority of Android phones. And out of my friend which have Android phones, I don't know a single one who has had their phones for over 4 years.
Feel free to ask follow up questions or roast me or whatever :)
There are many reasons, but here are some of the most important:
Feel free to ask follow up questions or roast me or whatever :)