Well, I have been inactive on the MSE for quite some time due to personal problems and as I came back I observed that earlier I could see on the profile on users that at what date and time they have been active last on MSE website.
The use of it to me was that sometimes the users answering my questions would not been seen for long time and then I would put bounty on the question if I was not able to fully understand their solution.
Also, a lot of times the questions which I had were already asked and answered on MSE and I would ask in comments when I had some questions in attempts of user or answerer. But if the user had been inactive for quite a long time I would pose a question linking that previous question as user might have deceided not to be active for a variety of reasons.
So, I think it was quite a useful feature not for just me but a lot of users.
So, why was this feature disabled?
Also, in case there are some chances that it might be re - enabled then I would like to vote positively for such a feature.