What happens when it rains, Andre? Do you pile the lot of your possessions into a dry sack before dropping it into the basket(s)?
The pannier basket is rarely used bare. There is always a bag of some kind standing in it, and the top can be folded over contents. That jute bag in the photo above is waterproof to an hour of heavy rain, and I also have one of those sprayed with Nikwax (stuff for waterproofing goretex mountain jackets and boots) which will shrug off the deluge for an unlimited time. Also, the local supermarkets sell plasticized canvas shopping bags of the same sort, and a local deli gives their own branded one away, so I have a choice of browns and greens to match the bike. Also, permanently on my bike is a very fine crepe de chine (you dirty boys!) bag that folds up tiny and is waterproof, for emergencies when I'm caught without a sturdy bag in the basket. Finally, if I'm in a desperate downpour, I can buy a sturdy plastic shopping bag at any foodstore I pass, or a huge frozen food carrier with a sealable, waterproof top (dunno what it costs -- always took one from home when the occasion called for it). Basil's Cardiff pannier basket is shaped and dimensioned to take the common European shopping plastics, or the big brown paper bag you can still see sometimes at rural American stores.
I'm not talking about touring, you know, just about keeping your stuff dry for an hour or two without the wretched inconvenience of unrolling those Ortlieb rolltops or unstrapping British panniers or saddlebags, which gets your hands wet and cold. With my arrangements I never take off my leather dress gloves.
Horses for courses: the carthorse from Basil over a lot of tracks is faster than the speediest thoroughbred from Ortlieb. In my town, at any of the supermarkets, by the time you've unstrapped a Nelson Longflap while you stuff gets rained on, I've chucked my stuff in the bag in the basket, flipped the bag top over to keep it dry, and am home, my bike dried off, and looking out of the door, saying, "Oh, those poor cyclists in their lycra, with their smart cycling-specific luggage, suffering under a little rain."
Far too much bicycle gear is far too specialized, far too pricey, totally useless and counterproductive in all but the very narrowest of circumstances. I probably own, or have owned and sold or gave away, a couple of grand's worth of panniers and saddlebags and other bike luggage, and that Basil Cardiff Pannier Basket is by far the most useful, most versatile, and longest-lasting bike luggage I've ever owned. I bought a pair and in September will retire the one which has given a dozen years' service and replace it with the unused one, and buy another to keep as a spare or for the extremely rare occasions when I need two. It still works but is starting to show a spot of rust here and there.
If you don't like the Cardiff style of fixed smart basket, there is an American collapsible type available that sits flush to the rear triangle until required, then is released and self-assembles, being held in position by the gear on the hinge in the bottom of the basket.
