Another factor is the light level. If you have a lot of days with rain or low light, like UK or many other places have, nets reduce even more the level of light entering in the house. Lacking of a lot of the dangerous mosquito borne diseases than tropical places have, the cons weight more than the pros. Would be seen as a better deal in California for example, where the extra shadow is welcomed.
And finally there is some inertia provided by cultural factors. For Dutch allowing everybody to see your room by default (don't have anything to hide here) is a cultural post-war thing also.
Maybe I'm just used to it.
Also it's not only like a cultural thing, I legally had to put screens in every window of my house before it was able to be occupied. Just an anecdote...
It's weird how we never question things like that.
Regarding light - leaving aside however much it blocks light for illumination purposes, what about seeing out? I want to look out of the window, not look at a mesh all but completely obscuring the view.
Our current windows pivot in the middle which makes a fixed screen impossible.
(They do have a "pane inside" mode which would let you put a screen on the outside but we're 3 floors up and it would be a bit tricky, not to mention inconvenient when the temperature drops.)
Because I want to let more light in?
Because things flying in is approximately not a problem anyway?
Seems perfectly fathomable to me.
(I live in London, occasionally a fly will come in and chill out for a bit before sodding off again.. fine? I've never had a wasp inside even. Our mosquitoes will extremely rarely give you anything nasty. Moths that would fly in aren't the fabric-eating kind. Even leaving aside the other issues, there's no reason to, it wouldn't be worth my time or money to buy them/fit them/have them fitted. I've spent longer writing this comment than being irritated by anything flying in through my windows.)
https://medium.com/@sophanemwise/the-wasp-killing-myth-in-ge...
Wasps are the usual example because it's legal to kill flies/mosquitoes and no one wants to kill the other protected insects like bumblebees. The wasps in Berlin are common and pretty aggressive, and have free rein in an awful lot of the chain backeries.
If it works or not I don't really know but at least I had a bowl of ice cream and wasn't especially bothered..
What I mean is, if this is a commonly believed exaggeration then it could just be that in this case the person believing it wasn't the wasp-killer (or would-be-killer) but the cafe owner. Has your friend ever actually been fined for doing it, or did the cafe owner/manager mention having had to deal with it in the past?
Certainly does seem odd that this law would (a) exist; and (b) be intended to stop this sort of behaviour; and (c) actually be enforced!
I would say mainly it's not enforced because b) has been effective - Germans (or Berliners at least) don't kill wasps! If doing so became common, it would probably be enforced more consistently.
However, there were also pretty much no bugs; we kept the windows and doors open regularly without an issue - if you tried that were I live now in the US you'd have flies inside making a racket and be eaten alive by mosquitoes.