Free drinks are not a given after delays of any length. However, whenever I feel so motivated, I simply ask the FA to see about the possibility of obliging and prepare myself for one of 4 scenarios:

1) "No, sir." I've never actually been declined, presumably because I only ask in cases where the airline has clearly screwed up or the delay was excessively long (3.5 hours, even if weather related, would probably prompt me to inquire).
2) They slyly comp myself and the people in my immediate vacinity.
3) After receiving approval from the purser/captain, free drinks are offered to all (sometimes just one/person).
4) No announcement is made, but no money is collected (from anyone) either. I assume this requires the same authorization as scenario #3, yet doesn't encourage abuse.

In the old days, #3 was the most common resolution, but I've seen a lot more #2 and #4 in recent years.