I agree most people will join with a utilitarian mindset and not an ideological one. Still, I think the world will give them reasons to join Bitcoin for practical purposes.

The most basic one will simply be to watch a chart where Bitcoin has been steadily (ignoring short term volatility) going up in value for decades.

Another one could be Bitcoiners being willing to only give/take payment in Bitcoin. That's a predicable thing that will probably happen gradually more and more and would force nocoiners to jump onboard to get what they want.