I loved Windows 7. I haven't felt that way about many of the Windows systems. I tolerated 3.1, preferring DOS and Solaris at the time. Windows 95 was great, with me skipping Windows 98 after installing it on a few PCs at work. I thought Windows 2000 was OK, and did really like XP. I avoided Vista, running XP until I got a beta of Win 7. Then I thought Microsoft had made a great move, slimming down the OS and making it faster on the same hardware.
I skipped Windows 8 and moved to Windows 10, so I guess I like every other version of Windows. That makes sense. I've often felt every other version of SQL Server was really good, with some slim, not quite sure I like this, not quite sure this is worth the money, in-between versions. That might be changing as I liked SQL Server 2016, 2017, and 2019 is looking good.
I ran across an article on the move to Windows 10, which Microsoft has been pushing and which as proceeded very well. Many people upgraded, especially with the free offer to upgrade. However, the pace of change has leveled off, with Windows 10 at 44% recently and Windows 7 at nearly 37%. The disconcerting issue is that the latter number has barely changed from the end of 2018. With Windows 7 expected to EOL in Jan of 2020, Microsoft is trying to push people forward.
There are all sorts of reasons people are loathe to update their OS. Compatability issues, the comfortable feeling of knowing how a system works, and certainly resource concerns. I wish security was a higher level of concern for more people. When Win7 EOLs, enterprises can pay $200/yr/machine to get patches, but there is no option for Home users. I think this is a little short sighted as many Home users might not see value in upgrading, but they (and the rest of us) need secure machines on the Internet. Why wouldn't a $50/yr charge for security patches make sense?
Modern hardware is powerful and lasts longer, so I could understand an individual that started running the OS in 2011 not seeing a need to change. They are happy with a PC that runs email, browses the web, plays solitaire, and manages money. Do these people need to upgrade to Win 10? I don't know that they do, and the vast majority of the world are consumers, not creators, so the much of the work done in Win10 isn't useful for them.
There isn't a right answer here, and certainly there are security concerns from an older OS, but at some point the OS and hardware will be good enough for most people to stick around a long time. Microsoft ought to be prepared in those cases to enable very long term support, perhaps with some yearly charge, to provide patches to the OS. I don't know if Win7 is the place to do that, but I do think that Win10 ought to be around for a long, long time with paid support.