The most-loved thing about a PowerPC Mac isn't its processor but the computer architecture. Some of the greatest and most iconic Macs out there were/are PowerPC Macs. Therefore, there is a strong fan base and hold on these machines to make them still useable today in most cases.
It's not necessarily nostalgia for me personally, but they are cheap and I find it fun using an old computer, but one that can still actually do things today. I'd be just fine if, for example, my iBook G4 had an Intel processor, as I really like the form factor of the computer itself... although there IS this nice feeling one can get from knowing that PowerPC processor is inside. PowerPC processors actually used to smoke Pentiums!
Personally, I didn't even have an Intel computer until 2011 or 2012 (I think early 2012) when my dad handed down his 2009 base model MacBook Pro to me. Granted, I still find myself using PowerPC Macs a lot. In fact, since I like desktop computers better and still enjoy using PowerPC Macs, I guiltily have my MBP sitting while I type this on my PowerMac G5. (I soon will get a cable to connect it to a monitor so it feels more desktop-like). However, the one thing that gets me is sentimentality... I almost feel like I am ditching PowerPC Macs if I go to Intel. I mean, if I use my MBP as a desktop then there would be no reason to use my G5. I could still take my PowerPC laptop/s places, but the MBP can easily be detached from the monitor and serve as an on-the-go machine. I did semi-ditch PowerPC once I got the MBP, as my iMac G5 was the best PowerPC Mac I had at the time and was only good for me as a secondary computer. I don't know, I almost feel saddened by the thought of 'ditching' PowerPC Macs as secondary-to-main machines, as there is still a fight to get them to work well today, and I am pro-PowerPC Mac in that sense. I also have many more PowerPC Macs than before.
Anyway, there is something about PowerPC Macs that still attracts people, other than the fact that the mid-to-later ones looked so cool and were/are a pleasure to use. Many have still stuck to a PowerPC Mac either as a secondary computer or even as a main one; some who started buying Macs after PowerPC had been phased out end up getting drawn to them. They are just hearty, timeless machines that some describe as having a "soul". That there is deep stuff, but you know what I mean...
----------
I know a writer who still uses a Macintosh IIcx with Microsoft Word 5.1 as her primary work machine.
She uses her phone for internet(email/social media/etc.) She had a more modern computer for internet use, but when smartphones became good enough, she just ditched the computer. Now it's her trusty IIcx. Dial-up internet for it for the sole purpose of emailing manuscripts to her editor.
Wow, I want to try that; that seems awesome! (too bad I don't have dial-up, which isn't something you usually hear people saying).