Temples are useful in several situations:
1) You need a culture pop to get a resource cheap and you either aren't scientific (cheap libraries) or don't have lit yet.
2) You are getting a ton of gold from somewhere and want to run 100% science, but will have unhappy people otherwise
3) You are playing for culture (20K or 100K)
4) You want to build 'em cause you are a total builder at heart.
5) You need 1 more content citizen and running 10% lux will give you more than 1.
6) One more content citizen will pop you into WLT(leadertype of your choice)D
Early in the game, I only build temples in a 20K game or if I'm religious and need a pop to get a resource. I do, however, build them.
Just having culture is useful in itself - a city with popped borders is harder for an opponent to attack, while making it easier for you to defend, if you have big culture, the AI treats you better, cities are less likely to flip.
One of the reasons culture is eschewed by players is that once you get to high levels, you simple cannot beat the AI in culture unless you throw everything at it. I played at 100K game on deity some time ago, and even with 100 cities or so producing culture, i was worried about one of my AI opponents keeping me from winning!!! Against demigod/deity opponents, they get huge production discounts, so they will build temples quickly and still out expand you, so you have to give up something, and culture is a weapon that is very hard to plan around. You can out research a high level AI, by known how it works, you can kill a high level AI with cats and armies - but it's hard to beat a high level AI on culture.