I have big, and I mean BIG commitment issues when it comes to finishing a TV show. Namely, I barely finish a season of a TV show, especially North American/English TV. I just can't explain why... um, I have a short attention span?
It's not like I don't have the time - if I really wanted to, I could easily cut back on sleep and watch a show, marathon a series in one go. But for some reason it just hasn't happened very frequently.
And then I thought back to my anime watching. In the past 2 months, I have successfully watched the entirety of Fate/Zero, Baccano!, and Mouryou no Hako (the last two were re-watches, though). Maybe it's the 30-minute timeframe that grabs my attention better?
Then I thought about the difference in story and structure - especially the ending of a show/season. North American/English shows (S1) are usually made with the assumption and hope that a S2 or more will be made, so season finales are often cliffhangers or some mystery. And the desire to continue and 'become successful' means almost every season finale is like that.
On the other hand, Japanese TV (including anime) are mostly made with a definite ending in mind. The audience goes in to a show expecting a clear ending that wraps everything up, a story that is self-contained. 'Success' of a TV show is not necessarily defined by a sequel/subsequent seasons.
There are pros and cons to both types of structures/ending - but I guess that knowledge of working towards a definite end appeals to me more than the possibility of longevity, only because that's the kind of media I've been exposed to most.