Based on trip reports I've read here, this is definitely one area where DL wins among domestic carriers hands down. On DL I can't remember a single flight where I was not offered a drink before take off in FC (although there was probably one or two, but it is definitely the rare exception). Even last week on a flight that was running late I expected the FA's to not serve drinks because they wouldn't want to slow down boarding, but sure enough, they still did, squeezing between boarding coach passengers to take our orders and serve our drinks!