the joy of this website is there are no rules (none that i have read and i actually haven't' read any of the rules) that require us to finish. the happiness of the various fans connected to the work can help promote/push you along i suppose. for me, I go at my own pace. I'm not a good writer, im very bad at grammar and i go around in circles. Sometimes i can pump out tons of words and sometimes i'll go months without having any want to write at all. then again, writing comes naturally to some and they can pump out story after story like some of the guys here.
i'm sure people urge the authors to complete their work, the side status updates people do that all the time. also the fact you mentioned you won't read their work anymore cause they abandoned a story is slightly childish, don't you think? there is also a rating feedback system, email, messaging, hundreds of ways to communicate.for me when i put up stuff whenever i do, i don't have a huge readership but i get the small amounts of feedback i want. Sometimes it is sugar coated, but there is the occasional person that will come along and actually really want to talk about the work with you, meanings, context, arguments etc.