I don't think the public nature of social media is driving this. After all people's private photo albums and slideshows back in the day were also heavily curate

I don't think the public nature of social media is driving this. After all people's private photo albums and slideshows back in the day were also heavily curated collections of "fake" happiness. I think the difference is thanks to the internet and the proliferation of smart phones, we are able to consume a much larger volume of these collections.