I was surprised to see the comment that stainless steel wasn't that expensive, so did some searches and found that the relative prices of materials has changed a lot since I last bought any a couple of decades ago.
Here in the US fiberglass is the most common and runs about $0.50/sq. ft. Aluminum next most common $0.42/sq ft. Next is stainless steel at $1.02 sq. ft. and finally the standard from early to mid 20th century, copper at $3.00 sq. ft. For you metric zealots remember you are only interested in the price ratios and that math is the same regardless of units.
Given those prices it isn't obvious why fiberglass is used most here. It is easier to work with (cuts with a knife and is very flexible), but is far less durable than aluminum. Stainless is not noob friendly but obviously one of the best in terms of durability. Copper is about like aluminum to work with, and is beautiful, but dang it costs plenty.
I also ran across a product that might be of interest to some, pet-proof fiberglass.
I don't understand why screens aren't used everywhere. In combination with exhaust fans they allow me to almost totally avoid air conditioning while not suffering from mosquitos, houseflies, bees, wasps and hornets. In an eco-friendly world they are one of the easiest and cheapest solutions. And while I agree that bees and wasps can usually be gently herded out, it is a nuisance and SWMBO isn't as tolerant of the six and eight legged sharers of our planet.