Why? What's good about it? To be good design something needs to look good and perform well. This product looks horrible and (absent proper testing) no-one knows how well it performs.
Good looks are totally subjective.
What it does achieve is a very clever, low cost, lightweight and likely disposable solution to those wishing to wear some form of lid when they rent a cycle.
Carrying a lid to work, or into town for a days sightseeing, is a major faff.
These things could almost be disposable and even branded I very smart ways.
Plus the Chinese lantern design is beautiful and equally simple.
Whether you like the product, or agree with its use, or not it... is a very neat price of design.
Your criteria for a "good" product is very narrow.
Do antibiotics look good, do VW beetles perform well.