Owning different bikes for different riding conditions is kind of like having different golf clubs for different shots. Sure, I could play an entire round with a seven iron and putter, but what fun would that be? Truth be told, I probably wouldn't shoot much worse than having all 14.

The same applies to having a rain bike, a winter bike, a gravel bike, a weekend bike, etc. I wouldn't ride my steel bike in the wet because I don't need to, which is why I don't put fenders on it. So even though you should be able to ride any bike in the rain, you really don't want to.