As mentioned by my colleague, this was done because of the caching in place you would have a topic with incorrect unread/read status so in fact, from our point of view, was worse as people may think they read something when they didn't or get frustrated when they read something it did not properly be marked as such. You're more than welcome to post a feature suggestion for this but at this time, this is the decision we're moving with. Sorry I do not have better news for you.