The reason is not technical. It’s economic and psychological. The Bitcoin system makes sense. Millions of people see its massive utility. They understand that Bitcoin is a very elegant solution – they have no reason to ever abandon it.
Even in a nuclear apocalypse scenario, assuming just a few nodes survived, Bitcoin would likely be rejuvenated. It would become a link to the past that people would want to maintain. That’s how sticky it is.
Every day Bitcoin remains online is good for Bitcoin. Remember that.