Re: Ordinary person here
I'm with you on most points, but with SD cards is not necessarily about changing them, but simply about having a reasonable amount of storage in the first place. My "16GB" phone actually shows as under 12GB, which hopefully means the OS is using some rather than it just having gone missing. In total, I've used up about 22GB of the 42GB I have available with a 32GB (which shows as 30) SD card. If I only had the 28GB or so a 32GB phone would give me, that doesn't exactly leave a lot of space to use over the next couple of years before I'm likely to replace it. If I actually want to put all my music on it, I'd already be struggling. If I took any significant amount of photos or video with it, I'd be struggling. If I wanted to install a couple of decent size games, I'd be struggling.
A lot of people reply to that sort of thing by saying that 16 or 32GB is fine, most people don't need more, just use the cloud, and so on. And that's fine for people who use their phones that way. But for those of us who do want a bit more storage, SD cards are basically the only choice since the options for phones with more built in are very limited, and usually quite a bit more expensive than the additional cost of a similarly sized SD card would justify (for example, a 64GB iPhone 6 costs £105 more than a 16GB one. A 64GB microSD card costs about £20.). A phone that can take an SD card caters for both groups. I've never changed an SD card in any of my phones, but I've also never had a phone that had enough storage built in, and a 400% markup on storage is pushing things a bit.