Perfect explanation.

Thank you, I try. It’s always tricky to keep network infrastructure explanations concise and readable - the Internet is such a complicated mess.

People like paying for convenience.

Well, I would simplify that to people like convenience. Infrastructure of any type is basically someone else solving convenience problems for you. People don’t really like paying, but they will if it’s the most convenient option.

Syncthing is doing this for you for free, I assume mostly because the developers wanted the infrastructure to work that way and didn’t want it to be dependent on DNS, and decided to make it available to users at large. It’s very convenient, but it also obscures a lot of the technical side of network services which can make learning harder.

This kind of thing shows why tech giants are giants and why selfhosted is a niche.

There’s also always the “why reinvent the wheel?” question, and consider that the guy who is selling wheels works on making wheels as a full-time occupation and has been doing so long enough to build a business on it, whereas you are a hobbyist. There are things that guy knows about wheelmaking that would take you ten years to learn, and he also has a properly equipped workshop for it - you have some YouTube videos, your garage and a handful of tools from Harbor Freight.

Sometimes there is good reason to do so (e.g. privacy from cloud service data gathering) but this is a real balancing act between cost (time and money, both up-front and long-term), risk (privacy exposure, data loss, failure tolerance), and convenience. If you’re going to do something yourself, you should have a specific answer to the question, and probably do a little cost-benefit checking.