Yep, if it ain't broke, don't fix it. I can understand if people are comfortable with what they already got and don't see a need for change.
I remember when Win7 was the big thing and a friend of mine got it and installed it on his computer. He was going on and on about how great it was and how I should get it. At the time all my computers were running Windows XP. For some reason he deemed that an affront to progress.
"But my computer works just fine now."
But Win7 is so smooth, everything works so well, yada yada, it's a wonderful thing.
"But my computer already does what I want it to do."
But you really should try it, you'll love it, blah blah.
"Look, next time I get a computer it will probably have Win7 on it by default, and I will use it and (from what I have heard) probably like it. But I'm not going to take my computer, which is working just fine and doing all I want it to do, and upgrade it simply for the sake of upgrading."
Currently all my computers have Win7... I usually run Linux Mint 18 from a flash drive, but the computers' hard drives have Windows 7 on them. So take the conversation I just related, change "Windows XP" to "Win7" and change all mention of "Win7" to "Win10" and you'll have my current policy.