People have different reasons for not updating. I have a 2010 Macbook Pro that cannot run the latest patch on High Sierra and I have to stop right before the last known patch. Otherwise the machine goes to an infinite reboot loop. Apple doesn't care for a 9 yr old machine. But it is otherwise a fine piece of hardware - use upgradable HDD, battery etc. I still prefer that to my 2016 Macbook Pro that is a piece of shit machine.