I "wore" all my babies, the first two with traditional "baby bjorn" type slings. With my youngest I used Kari me's (I think that is how it is written) and I had to have two, my first being purple, I had to buy a second in black as her father also wanted to carry her and felt a bit daft with the purple one.
It is a great way of carrying your young, makes a lot of sense when they are very young, and they enjoy the cuddle, leaving you free to use your arms! On the other hand, as one poster says, if you breastfeed, it is discreet and baby has lunch on tap!
It has been used throughout the world, i believe on all five continents - puschairs and buggies have only been around for the last couple of hundred years, if that.