Bandwidth isn't necessarily the best measurement of "what the internet is used for", for example porn may stream in lower quality on average, maybe more people hoard porn (download once, watch many times) as it's probably easier to remember the name of your favourite film than which random site to find your favourite porno on, plus the porn category includes pictures as well as video.

But I guess what the best measurement would be is subjective anyway, plus it's not so easy to measure anything like "amount of time spent doing X" or "number of people doing Y". Alternatively it's a valid opinion to have that bandwidth is the best metric, it's just not my opinion.

The thing that is interesting to me is that for a very long time, "Adult content" was what the vast majority of internet bandwidth was used for, by a tremendous margin. I remember in '01, one of my co-workers streamed CNN, after the twin towers disaster; In spite of working in the industry for several years, that was the first time I saw someone use streaming video over the Internet for anything other than demos (and pornography)

The fact that non-adult streaming video has surpassed adult streaming video (in terms of bandwidth used) is interesting because it means that the Internet is now a mainstream distribution channel for mainstream video.