Why do some threads get replies and others don't?

About half the threads on this board never get a reply.

How do you decide which to reply to and which not?

Sorry to reply you so late, We have to serve too many customers every day,
and we can’t reply to your questions in time even omission. Hope you can
understand. We are terrible sorry, but don’t worry, we will do our best to solve
the problems you encounter in the use of the product.