[strong dislike for single speed bikes, rhetorical “what’s the point” question]
To me at least, any particular style of bike or cycling-like-activity needs no more justification than “it’s a different experience, and folks enjoy it”. Where’s the harm? Have your fun on actual half-bikes for all that I care, I might laugh at your goofy different-from-my-interests shit but if you’re out there and happy then I’m happy.
Even assuming you live somewhere with a strong enough cultural delay that the fixie craze is still around 2007-peak levels of annoying trendiness (try Brazil sometime), it still means more people on bikes. Which is positive thing for road safety and overall future-of-mankind purposes if you ask me.
And it’s not like geared bike tech has stagnated for lack of interest. I just paid US$ 380 (plus shipping and an absurd amount of import taxes, but that’s another, tiresome story) for a current generation Shimano 105 group that’s, judging from many reliable accounts, not a million miles away in either performance or reliability from circa 2006 Dura Ace with a corrected-for-inflation MSRP of US$ 2300. Certainly the cheapest I’ve ever seen for that level of kit, which came in handy as I’m in the middle of my first-ever modern road bike build project. Yay!
It’s a good time to be alive as a bike nerd, it’s what I mean. And that goes for fixie kids, crabon fiends, retrogrouches and frankly everyone else who cares about such things.