I would've kept my iPhone 5 64 GB if stuck with a current gen 16 GB device.
128 here, 64 is manageable, but everyone's needs or preferences are different.
Who cares what storage capacity someone else has? I bought the 128GB and I'm a 5'4" scrawny chick. Does this mean I am now an alpha female?
I bought it because I take tons of pics and video and I tend to keep apps around that I never use. I can't be bothered to delete stuff. When I noticed my 64GB 5s was nearing capacity and I had to delete a few things to update the OS before the 6 plus came out, I said to myself "Self? You need that 128GB."
So, I bought it.
It was that simple. I never stopped to wonder how much street cred it gave me or if others would think I was excessive for getting the 128GB. I got what I needed. If the OP only needs 16GB, then that's what should be purchased. I wish that's all I used. It would save me 200 bucks each time I update. I've not had a 16GB phone since the iPhone 4.
I don't store a lot of pictures, music, or video, and I don't like a lot of apps to meddle through. I keep only the core that I need and the rest come and go, especially with games.
No reason to be ashamed, but it is a poor purchase decision. Apps, photos, videos, etc are all going to take up more space than before because of the increased screen resolution (3x vs 2x). That's roughly a 50-100% increase in overall usage (assets need to be larger, you'll be recording video at higher frame rates, etc). As great as cloud services are becoming, local apps (and iOS) are becoming larger in size. It's $100.00 to go from 16GB to 64GB. Your choice is obviously yours and personal, but it's economically and practically unwise.