For the most part, I can live with the "non upgradeable" factor of the newer Macs. I always did like to be able to easily get under the hood, as I keep my computers a fairly long time, but.... I could theoretically give that up for smaller, lighter designs.
But... this RAM factor essentially resulted in my not buying a shiny new laptop this season. Not that Apple is probably dashed or anything by it
Reason is, the 13" with 16GB of RAM is not available immediately, and due to travel I needed to be able to get one within a week or so. If they were upgradeable, I could have simply bought the one with 8GB of RAM. It's available, and.. heck, I might not NEED more than that. BUT... what if I do? Since there is no way to add it later, if/when I do want it, I feel like I "have" to get the 16GB when I buy it, just in case. And they are a couple of weeks out, which can't work for my schedule.
Not really germane to the thread, but perhaps answers your question about why someone would get 16GB when they may not need it. There is no way to "try" 8GB if you think you might EVER want the 16GB. I'm still wishing I had been able to pick up a computer yesterday during the sale. Hmmph!!
(Instead I bought a Black Friday SSD for my older MBP 13")