Threads with high reply but no conversation

File: dead_thread.jpg (32KB, 432x576px) Image search: [Google]

32KB, 432x576px

Im somewhat new here on 4chan (a year maybe).
I noticed the following:

There are threads where OP askes other anons to reply with something.
e.g. on /b/:
>ITT: we describe our sex live with movie titles
or on /g/:
>Screenfetch thread ! Show your screenfetch
Or the OP is asking for something related to the Lives or Person of the other anons.

Those Threads have a high reply rate but nobody is replying to each other.
Everbody is only interested to tell something about him/her self and it looks like nobody is reading posts.

Another example is currently the ylyl threads on /b/

What are those threads called? Are those indeed dead thread ?