Note: it is just a suggesstion.
Like, i mean to say there can be a section of date of post after the line which i draw in the picture.
Your suggestion is not out of place. But I think the most important application of your suggestion is to prevent bumping older threads and there is a mechanism to check that. If you are about to post in an old thread you would definitely be notified that the thread is more than 120 days old and as such you should consider starting a new topic.
Secondly, when conversations start flowing in a thread, the emphasis is no more on the Op rather on the successive posts on the thread. So, the date of the most recent reply is more important than the date of the Op and this just helps much in sorting of the posts.