Why is everything - not just iOS - so bloated these days?

Deploying stuff from Unity to Android is a doddle. It's almost drag-n-drop. Create an apk file and hit "build and load" and as if by magic your new app appears on the connected device (provided it's plugged into the USB port, and USB debugging is enabled).

But, in short, it's easy.

Deploying to iOS is a whole different story.
Not least of all because of all the messing about with certificates, provisioning, requests for certificates and all the other junk that goes on. A very good and comprehensive guide to deploying to iOS can be found here - http://gamasutra.com/blogs/ThaleiaDeniozou/20140826/224186/Export_from_Unity_to_an_iOS_Device.php

As we found a few years ago, deploying to an iOS device from anything other than a Mac is real pain. It can be done. We even managed to generate our own developer certificates using a Windows 7 machine, but it involved lots of manual processing and script-bashing to validate Md5-hashes and build files from the ethers.

This time, as we did then, it was just easier to boot up a Mac.
And download the iOS compiler.

As much as we've grown to hate Microsoft (seriously, first .NET, then Windows 10, then the unholy alliance of a .NET Visual Studio hacked onto a Java-based developer-  Unity - running on Windows 10) this just shows that there's no viable alternative.

280Mb vs 4.2Gb?!
I'm not sure that even Apple could justify that amount of bloat....