This has been a pretty nice discussion all in all. I am one of those people who embrace the idea of "citizen science" because I do not have the expertise to be a researcher. However I am intensely interested in seeing that the basic research is done so it can be built upon by others. I am also interested in the humanitarian aspects of this research, which probably would not get done if not for projects such as this.
I started with a single P4 and gradually acquired various other systems for little or nothing, gradually replacing the least efficient with more efficient machines as they became available. A couple of members (brinktastee and nanoprobe) were kind enough to supply me with some surplus hard drives they had so I could put more machines to work and replace hard drives which died. The limiting factor now is how much I want to spend on electricity and to not overload a circuit.
Thus, all of the various metrics ( points, results, time, and badges) are not the reasons I participate, but they do allow me to attempt to tailor the various projects to the most appropriate machine.
Your points are interesting as is the discussion. Whatever your motivation, thanks for contributing. Crunch on.
Cheers

Well, like many people here, I've also been here long. Also I'm not here for a quick change to NEW hardware, as it has to be shown proven for WCG.

I used to run at my home:
- laptops Lenovo T60, T61 & 2x Dell...all dual cores!
- dual-P2 system with only 2x 533MHz...belive me or not, it was great till they killed WinXP! & still I'm selling replacement board on eBAY, mine original one is MODDED.
- old P3 Tualatin, which was also great for 2nd computer. That board was sold somewhere in Singapore for $100 with RAM & CPU, as it was one of the proved stable boards for factory machines PCs.

From there I've moved some generations ahead to running:
- all thos laptops, except T60 - which I have to service these days.
- Android device that was given to my on a work, but I quickly replaced it with iPhone
- 2x Q9400S on Ubuntu, which I run to spend less electricity
- 1x X3210 as a main computer, from which I write to you. Strangely, but Win10 works on Xeons, even on unsupported families of CPUs.
- 1x X3360 as 2nd computer, as the Q9550S will not boot on Win10.

Pretty soon I'm going to make an investment from Gridcoins, the ones people laughed here about, to some used workstation which should have at least 12 threads or more. It will not be the newest one, as the new ones cost about 4.000€. This will be the 500€ ones, that will do the job well.

Also, I'm using my GPUs on SETi@home, as GPU grid is not viable for my list of graphics:
- 2x GT 730, as one is one of the fastest on PCI x8 extension slot
- 1x GT 1030, as I haven't programmed the Ubuntu to watch temps, so I opted for a slower, low power graphics.
- 1x GTX 1050Ti for my 2nd computer, which is only to play Mass Effect Andromeda, from time to time.

So, why would anyone use new computer now? They spend less energy?
NO, they don't. Maybe if you don't run WCG on them, but they do spend about 15-20W per core when pushed.
It's good for me?
How? Energy consumption is the same. My computer works just fine. Writing to you even with SETi@home running graphics. No problems in slow-response. When It gets slow, I'll replace it!
It's good for economy?
Well, yes. But what do I have from economy? I'm not paid by either manufacturer of hardware or software. So why change?

It's going to continue to run 24/7, as long as RAM, CPU & MBO will hold. And all my RAM has a life-time warranty!