First the selling point was that "the USD can never be a reliable store of value because it's evil fiat currency controlled by a central bank, use Bitcoin instead!". This has quietly faded as the volatility of Bitcoin continues to exceed that of the US dollar by orders of magnitude.
Then it was about "decentralization", another argument that went away when people realized that Chinese mining pools control the whole thing.
Then it was all about the low transaction fees and freeing you from the tyranny of payment processors, until the fees went higher than PayPal, and now /r/Bitcoin will call you stupid for complaining about fees.
I don't even know what the current arguments in Bitcoin's favor are anymore, but I'm sure they'll be different next year.
And of course, in all of these cases, there's never any acknowledgement that the shift happened - "We're at war with Eurasia; we've always been at war with Eurasia"