I build app for iOS debug, .ipa file size = 11,696 KB, however I then build the same app for release = 75,464 KB.
For comparison on Android:
Android release .apk = 3,433 KB.
Android debug .apk = 3,913 KB
Why are the iOS files sizes so vastly different ?
You can actually see how big the files are. Rename the .ipa to .zip, then upzip the archive. You can then examine the files in it.
It will be interesting to see what you find!
The difference between iOS debug and release:
Debug Folders = Payload (37,025,216 kb)
Release Folders = Payload (35,741,441 kb), SwiftSupport (151,053,296 kb), Symbols (1,750,096 kb)