'after' and 'before' express the same type of time sequence that past perfect 'had' expresses. They tells us two events took place, and that those events are connected in time, one having taken place before the other. So, speakers tend to merge the past perfect with the simple past in those contexts:Originally Posted by hela
I smoked forty cigarettes a day before I gave the habit up.
There were angry exclamations after the will was read.
The underlined portions represent the events that happened first. Note the scope: 'before' heads 'I gave the habit up', but its semantic contribution is to tell us the event 'I smoked forty cigarettes a day' happened first. 'after' heads 'the will was read, and its semantic contribution is to tell us 'the will was read' happened first.
Both 'after' and 'before', as well as 'had' share the same semantic function. They connect two events in time, which means 'had' is pretty much redundant in those contexts, and the reason the simple past is used.