ST
I think this all must go back to the old days of cinema, well before the time of a multiplex. The assumption was that you
knew which film you were going to see
,
as it was the only one on
! 
Of course nowadays it's fairly easy to go into the wrong one when there are 10-20 on offer! 
I suppose in the pre-1990s era it was the only chance for the Director, Producer etc getting any credit. If they stuck them at the end of the film the auditourium would be empty by the time their names came up! (Most people leave when the end credits start normally).
I have noticed many TV programmes adopting the same principle these days. Both Corrie & EEnders credit the producer/director/writer at the beginning now (which was almost unheard of as little as 6-7 years ago).
Of course nowadays it's fairly easy to go into the wrong one when there are 10-20 on offer!
I suppose in the pre-1990s era it was the only chance for the Director, Producer etc getting any credit. If they stuck them at the end of the film the auditourium would be empty by the time their names came up! (Most people leave when the end credits start normally).
I have noticed many TV programmes adopting the same principle these days. Both Corrie & EEnders credit the producer/director/writer at the beginning now (which was almost unheard of as little as 6-7 years ago).