If 16GB isn't enough, you will be stuck with an expensive device that doesn't meet your needs.
I understand your point, but ever since switching to Apple 4 years ago, I've never run out of storage with 16GB. I've never even gotten a notification saying that my storage was running low.
Keep in mind your phone's OS often eats up ~4GB. On a 16GB phone, you'd be left with only 12GB for personal storage.
With the current way I have my iPhone set up (it's been this way since I got it, basically), I only use, on average, around 5GB of data all-together. 12GB seems like it would be enough for me.
Streaming music uses A LOT of data.
I do not stream my music. I listen to most of my music from a computer. I only sync certain albums to my phone and rotate them occasionally, but I'm never really in a situation where I would need that much music on my phone at one time. I have maybe 20 albums tops, and I only keep 5 or 6 on my phone (honesty, the other albums would be skipped on shuffle mode anyway, lol). My current music library on my phone takes up 1GB :)
I upload photos that I take on my phone directly to Facebook and Instagram and then delete them, so I have 0gb of photos stored.
You're probably thinking "Well, if she doesn't store photos, have games, or listen to much music on her phone, what the heck does she need an iPhone 6s for?" Good question! It does seem like I don't use my phone, but rather, I don't use my phone as a storage device. I use my phone for a lot of things, including:
I don't really consider "resale value" as I tend to keep my phone a lot longer than two years. Resale value doesn't mean much if you keep a phone for 4+ years, lol