I don't know about your childhood, but when I was a kid, around the pre-K and Kindergarten age, I actually used to share toys. Granted there was always stuff at school that was the school's property and that was pretty much game for everyone, but there was also stuff that people either brought to school for show-and-tell or sometimes things that they just brought for kicks. Either way, I certainly remember even borrowing and bringing home other kids' toys for awhile, before bringing them back.
What if it were like that today? By my age and beyond, most people don't really like sharing things. If we're being totally honest, I'll pretend I don't have extra pens if you ask because I've given so many out and ended up never getting them back (or worse, I do get them back and discover you've been chewing on them for the past three hours... gross; buy your own pens). Most people are so protective of their personal belongings that they won't let them out of their sight!
Would you let someone borrow your phone for a day? Laptop? Car?
Short aside for the car issue. Sophomore year I was going on a first date with a girl, and back then I was not privileged enough to have my own set of wheels. One of my roommates at the time, without even thinking, offered me his. It was a manual, and I had only driven manual vehicles at work before (that were not cars) and even after me telling him that, he shrugged and told me that if it were him he'd want to be able to pick up the girl and take her out. I don't know if I've ever told him how much that meant, but it did and had a lasting impression on me. As I'm living with him again this year (after being abroad last year) we have swapped cars before so we could do things like bring his boat down to Clemson and such. Though we've only known each other for three years, we have an impeccable bond of trust between us. I value that.
I think we are all really concerned with losing what we have earned and worked so hard for. Especially when the price tags on our "toys" begin to exponentially increase, it gets harder and harder to let it out of your reach and into someone else's. The interesting thing though, is that this sort of distrust of society developed. Naturally, when we were young we didn't know any better, and were happy to oblige to let our favorite toys visit another's home. However somewhere along the way, that mantra changed, only to be replaced by the current cynical and skeptical me.
Today, if someone needs your help, give them the benefit of the doubt, and let them borrow what they may need (even if that something is your time). While the saying "sharing is caring" is cheesy, it actually "can beeeeee, fun."