iOS user here with my iPhone 5. Have owned an iPhone since the 3G (which I think was 2009).
I also own an iPad 3 and a Macbook Pro Retina 13' which is my main machine currently.
As for why? Multiple reasons why. Please keep in mind I am not trying to convert you, I believe in "Use what works for you". Im just telling you why *I* choose it:
The ecosystem surrounding the iPhones/iPad:
The ecosystem surrounding a device is a huge factor in my purchasing decisions. I have had people brag to me about their other device, it has higher specifications whatever. The thing is, if any company is going to make anything, whether it be a simple cover, a specialised app, an embedded system like a car stereo, a tablet mount etc. You KNOW they are going to make it for the iDevices first.
Warranty/Replacements:
If you havent noticed my profile, I am currently living in Tokyo Japan. If I have an issue with any of my iDevices that are currently with me (iPhone, iPad or Macbook), I walk in to the local Apple store here and I walk out with a new one, even without a receipt and in a different country. I can even get the US keyboard (as they carry them as well) on my Mac instead of being forced into accepting the Japanese keyboard. Zero downtime. Same thing applies if I lose one of the accessories (not so much a problem with modern Android chargers now days since its all MicroUSB, but with the laptop, chargers can be a problem. Any apple store here has my charger).
Why I choose iOS/OSX apps:
iOS apps have a certain level of polish expected of them. While there are plenty of polished apps in the Microsoft and Linux world, it is not expected of them. iOS/OSX app developers believe that simplicity is the ultimate of sophistication and less is more. Sure, many iOS/OSX apps are paid and there are many free alternatives on Linux/Windows/Android, but again, being paid, there is a certain level of polish expected which tends to make them "just work" (to use that ol cliché). I find many Linux/Android apps tend to be a University students pet project and they'll fix the bugs when they arent busy studying (I know there are plenty of solid apps, but much of is very 'hacky').
When I first went 100% OSX (As my main Windows machine is back in Australia), It irked me slightly that the majority of the apps were paid whereas the Windows app might have been free. But after learning the apps were so damn polished that let me just use them and not fight them/fix them, I 'got it'. Ive probably spent about $100 on software to get the machine exactly where I want it and all of it works beautifully. So much time saved not messing around with the software and just using it. As a tech, I have the skills to fix Windows things, I have the skills to fix Linux things, I just dont want to. I want to USE them, my time is worth too much to mess around.
App Reliability/Walled Garden:
I find the iPhones tend to be more reliable than their Android counterparts. When a developer creates an app for an iPhone, they need to to test it on the 2, 3G, 3GS, 4G, 4GS and the 5. These all have expected specifications, the screen sizes are known, the software they are running is known. You make the app work on these devices and you have pretty much got it covered.
With Android, there are a HUGE amount different devices, many different specifications, many different screen sizes to mess up the layout etc.. Of course the developer will test on the main ones like the Samsung Galaxy's, but its very difficult to test on all variations.
This guy here is an app developer for both platforms and has pictures of all his Android test devices vs a few iOS ones. Not only that, but people such as us techs mess with the core parts of the OS resulting in things the App didnt expect and sometimes crashing.
The dreaded "walled garden" of Apple doesnt allow you to get into the core system stuff. Kind of annoying for people like us who like to get in there and get all hacky, but it does help ensure the apps and OS is going to be really stable because again, the code knows what to expect and will always play nice with eachother.
While iOS has a walled garden, the OSX world is not. Even less-so than Windows. Dont forget that OSX is essentially Unix, if there is something I dont like about the operating system, chances are I can get into the code and change something with terminal or a text editor (and I have already).
I dont expect many techs here to understand or even like this way of thinking as getting into things and messing with them is what we do. Its how our minds work and I am like that as well. However, other times I just want to get work done and be effective. I want things to work exactly like they are supposed to when I need them. Thats why I like the iOS/OSX environment.
Its not perfect, there are a few things that irk me, but its pretty damn good for someone wants to just use it and not mess with it.