I really dislike auto-playing audio and video as well, for all the reasons you mentioned, but also for a less logical reason: it just makes it feel like the browser isn't on your side. If a site is automatically playing audio or a video advert, its design is not in the user's interest, so in that situation your software has to choose whose side to take. I just want and expect the software I have installed on my computer to take my side, and always act in my interests. It probably sounds silly but I just think software should always be primarily designed for the end user.