5kg for a chair isn't lightweight when compared to ordinary plastic chairs. And the pic where the guy is sitting at the bus stop is just plain stupid. While they are practical from storage point, no one is going to carry this to catch a bus.
Also, how about these-
Light weight and cost about 10 dollars
You love this option with great price. because it fanciful, we don't we don't tend see the cons, though I like it but my question is my comment how durable is it this could be what you are considering too