I don't know, do you know why twitter is not having edit post options. Thinking about this feature from last 3 and 1/2 years. Why twitter is not having edit post option. Only not me I think lots of other people are also looking for this feature.
Reason to looking for this feature is very simple. We are human and humans are always makes mistake. But there is no feature to edit mistake. I don't know twitter will launch this feature in coming time or not. But really we need this.
Hope twitter will launch this feature soon. For now enjoy twitting without making mistake.
Happy Twitting :)