It is user replaceable. You can buy the part and the tools and do it yourself if you're handy with a screwdriver. It's not a simple matter of snap-out/snap-in, but it's not much harder than replacing a car's windshield wipers, and much easier than something like replacing tires or brake pads.
I've done this on many phones. The phone often isn't the same as it was initially because it was not designed for this. Many phones have tape that has been adhered through the use of heat. Changing the battery requires removal of many screws and disassembling very sensitive parts. Little mistakes can make the phone inoperable.
Not to mention you take it to a technician who has the tools and you'd assume is doing a good job right? No, often it's some high school kid who is not invested in doing a good job but rather just getting it done. It's sloppier than if you were to do it yourself. So you have to resort to buying hundreds of dollars of tools and taking painstaking hours to get it done right and even then it might not turn out.
To the other posters who argue'd that we make a choice about this - no we really don't get a choice. If you want a cutting edge phone there are simply 0 options with replaceable batteries. This is planned obsolescence in an age where my several year old Motorola works just fine for my needs.
Certain phones can be done with a cheap kit. Some require heat guns (for certain adhesive tape) and more advanced equipment. Plus if you don't want to take any risk you really should have an anti-static environment with proper grounding.
The car is a good analogy.. As @mikeash said, it is replaceable, you just need tools, parts and expertise (and time and willingness). Same as replacing parts on your car.
It is just as user replaceable as those car parts, if not more so. It requires only a few cheap tools, some time, and maybe watching a YouTube video example before starting. I'm generally more comfortable dissembling my phone than my car since the consequences of messing up are much smaller.
have non-replaceable ram and cpu is one thing, but a part that is known to deteriorate with age and usage should be user replaceable.