First of all, we can still do this. Second, we tend to remember our childhoods as "the good old days" in an idealistic mental picture that could have been painted by Thomas Kinkade. I have some great memories from when I was a kid, but I also have some really bad ones that I will carry for the rest of my life.
However, let's go back to the whole "those days are gone forever" mentality I see so many people respond to my picture with. Those days may be gone, but it doesn't mean we can't get them back. We can teach our kids the joys of swimming in the creek instead of sitting on the couch or how to catch lightning bugs instead of Pokemons.
Our problem is that we have been so completely and utterly sucked into a culture of materialism that we are almost unable to disconnect from the machine we are part of now. We've traded our time with our kids for new cars, HD televisions and the latest "must-have" item. We don't let our kids run outdoors because we can't be there to supervise them because we're at work trying to make the money to pay for the electronics we use to babysit our kids while we are at that very job that keeps us from our families.
The media constantly runs scare stories which keep people from letting their kids doing anything fun and in between "news specials", we have advertising which has us believe that our lives are not complete without whatever it is they have to sell. Yet, the more we consume, the less free we are. We are giving up liberties and memories in exchange for a false sense of security and fulfillment. There is no money for companies to make off taking your kids to fish in the creek or teaching them how to make a garden or bake a loaf of bread from scratch. They actually stand to lose money if people were to grow or procure their own food.
I listen to folks who say they don't let their kids play in the yard or down the street "because it is too dangerous". 20 or 25 years ago, you'd see children outside, now it is a rare occasion to find them outdoors at all. Our world has always been "dangerous" and it is far more scary now, not because somehow people became more twisted and evil in one generation, it got more dangerous because we stopped getting involved in our kid's lives and in our neighborhoods.
The answer is, work less, spend less money and stop trying to make your child's life "perfect" by giving them every material thing. I see so many people try to ensure their kids or grandkids have "everything we didn't have as kids" that they forget that they should be focusing on giving them what they did have as kids. Don't worry about giving your kids the newest and nicest clothes or gadgets, spend time with them, help them create memories. Those tend to last much longer than the latest iPhone.