Comment by girvo

My reasoning is because once upon a time, I was using Macromedia Fireworks, and PNGs gave far far better results than JPGs did at the time, at least in terms of output quality. Nearly certainly because I didn't understand JPG compression, but for web work in the mid 2000s PNGs became my favourite. Not to mention proper alpha channels!

...and so it's stuck, two decades on haha