First of all: US patent law forbids making or using patented inventions, even for personal use. These days, this is usually for a period of 20 years.
Why do we get this wrong so frequently? My theory: it's caused by conflating patent law with the fair use doctrine of copyright law. Certain uses of copyrighted material are considered to be perfectly legal "fair use". There are four factors used to weigh fair use in copyright:
1. purpose and character of the use
2. nature of the copyrighted work
3. amount and substantiality
4. effect on the market
The "purpose and character" factor specifically includes whether the use is commercial or non-profit. And of course the "effect on the market" factor focuses on commerciality. So, if you have a non-profit use of a copyright that's not significantly impacting the market of the copyrighted work, you often have a strong claim to fair use.
Here's the rub: the concept of fair use applies to US copyright law, but NOT to US patent law. I'm not sure why this is, but I think that's the source of the frequent confusion.
Internet armchair lawyering aside: litigation over someone making a patented device for personal use is extremely rare, and usually not cost-effective. The worst I've ever seen, in almost two decades on forums, is a patent owner complaining to a forum admin about someone posting a how-to about making the patent owner's invention. It is almost never worthwhile to sue over this type of hobbyist use.
I believe there is also another nuance regarding making patented inventions solely for the purpose of research, but I would need to confirm this with an IP lawyer before understanding it fully. Let me know if anyone knows more about this.
I agree with all of your other points. The vast majority of patents are expired, searching patents is a great way to get ideas, and - in a healthy society - the government wants people to examine all of the public patent documents and drawings so that we can advance each others' inventions.