This was probably one of the last times this baby was carried around like this. Normally, babies are strapped in with their legs tucked in and not, as in this picture, completely vertical.
This is the preferred method for baby transportation for the majority of Tswana women. Additionally, I think it is a way of getting children accustomed to being in tight, hot spaces so that taxi rides later on in life are manageable. I am not sure of the mechanics of how they are able to fold that towel so it supports the weight of a baby. All I can say is that it works and to a high enough degree to entrusts a baby's safety to it.
I might be happy to be leaving this aspect of Tswana culture behind if I had to regularly carry around babies but I simply am not required nor have I had the desire to carry around any babies and if I did I might want to use some other device anyway. I might also be happy to say farewell to the practice if I were a baby because it looks damned uncomfortable despite the benefit of not having to walk anywhere. In the end, my opinion is swayed from indifferent to somewhat sad to not seeing this regularly because occasionally it provides a little chuckle.