The lore of many cultures tell the tales of superhuman beings walking about in the guise of mortal men. The storytellers did their best, using the framework of mortal understanding available to them, to explain why they would do such a thing as to slum with the little people. All told, it's just part of the pattern in a long tradition of people trying to make sense of things outside their normal experience.
The majority of our modern superheroes are almost automatically expected to maintain the secrecy of their private identities. Over the years, some have gone to complicated lengths to do this. A rare few have had the added complication of additional identities, some costumed and some civilian. A few others have managed to keep distance between their public and private interactions (Spiderman dates from different circles than Peter Parker), but others haven't done as well. Superman and Clark Kent have a lot of the same close friends, for example. Over the last couple of decades, a lot of people have made decisions to have superheroes either stop keeping their secret from those closest to them or revealing themselves to the world-at-large. Seems that people want to keep pulling their masks off.
I've never found myself to be in agreement with such choices. It may be a result of growing up in an era where superheroes guarded their secrets with almost fanatic dedication. Gradually, society has come to shoot down the idea of people having any secrets from loved ones. This has resulted in some costumed adventurers spilling their guts after a couple of dates instead of waiting till the relationship got really serious (Barry Allen didn't tell Iris about how close she had become to The Flash till their wedding night). It has also shown us close friends and lovers taking offense at having been lied to for years when they're finally brought in on things.
Really? As though it was any of their business. Now, if I were a close friend of someone like Peter Parker or Clark Kent and they were considering telling the world about their whole dual identity lifestyle, I would certainly appreciate some warning if not consultation before I found myself a target of reporters and vengeful villains. Otherwise, if they're keeping things secret, that's their business. If they miss a few lunches or have to run late sometimes with only a lame cover story, that's OK. Friends understand.
I can't imagine that writers are trying to remove points of potential conflict. Maybe they just don't like the idea of privacy anymore. Maybe they don't believe in the ability of their characters to sell the dual identity concept anymore. My feelings on that were echoed quite well in "The Dark Knight". If you think that one of the wealthiest men in the world is dressing up as a bat at night, leaping off skyscrapers, flattening police cars and beating criminals senseless by hand, threatening to expose him is probably not in your best interest. Likewise, people have long poked fun at Superman over working sans mask and expecting a pair of glasses to keep people from recognizing him up close. I've always said, if it works, good. If he thinks it works and it doesn't, humor him. Not only do we owe him at least that much, but who wants to piss him off about it? Don't poke the bear.
Unless you're secretly able to fly out to deflect asteroids yourself...? Is there something you want to share?