On the other hand I've been buying only refurbished electronics for a couple years now and have had no problems.
You really can't get away with that with laptops or desktops because the need for fans causes a lot of component wear and environments are so divergent you can't trust used sellers to not have a lot of the internals damaged. Or the keyboards and trackpads - heavy wear or use or just abuse and one damaged key can ruin a purchase.
Phones are nice and self contained enough that looking at the outside generally tells you the condition of the inside.
I've had luck buying laptops (specifically Thinkpads) previously owned by companies and being replaced by lot. Probably due to a mix of better environment, better treatment by workers and more likely to get fixed if broken.
I just recently bought a Thinkpad X1 Carbon on eBay. As a mac user I was shocked to learn that I could get a very capable device that was sold for € 1500 - € 2000 in 2013 for € 300. In great condition.
It doesn't say anything about the condition of the (now commonly non-user-replaceable) batteries and the battery longevity. The device may not have any scratches or dents, but the owner might've used it primarily to watch videos and play high-intensity (graphics wise) games most of the time. Those actions make the battery a "needs to be replaced sooner" thing (or worse, make the phone a "needs to be replaced sooner" thing). Even checking the battery cycle count is inadequate because it doesn't say how quickly the drain happened during use (that also impacts battery longevity).
I don't buy used myself, but it surprises me to hear that you avoid used desktops. I generally buy my workstation equipment new and keep it for a very long time. Yes, the fans need periodic servicing (e.g., a thorough cleaning every couple of years), or outright replacement if you don't keep them clean. But desktops are easily user-serviceable. If I were to buy used, it seems replacing a few bad fans would be easy.
The variability in the state of the hardware you get is much wider in notebook and desktop hardware because there is just more circuitry to break and more moving parts to wear out.