Does it serve a purpose to slowly run out the cards after players are already all in preflop?

We need to show the flop, then turn, the river sequentially. We are already all in, there will be 0 actions from this point, just give us the next 5 cards.

Yes, I agree...seems absurd to add drama to a $1-2 game at a local casino poker room, without the TV cameras on.

I like that they run them out that way, what's the hurry?

In TV shows it is needed to make it more interesting for viewers. In the local casinos the only reason i see to do it is to be sure that everybody on the table have seen the cards and hand is played correctly. I have personally seen few cases where the dealer does not see correctly the outcome and for example pushes chips to one of the players at the end in split pot situation. In this case other players interfere and correct him/her so maybe this slow roll is to give time everybody to see the development.

go all in and hoping the bluff is goog

Yeah, well, and where would be space for at least a little drama? Come on, you can wait those couple of seconds - your stack destiny is at stake!

If you are so much in a rush, you should try zoom poker on PokerStars!

Just chill and enjoy the thrill otherwise