On the overwhelming majority of UA & UX flights where I have not been proactively offered to-order PDB of choice, I have received my to-order choice upon request. My approach is as follows: "I know it's super busy before we take off, but if there's time, I would really appreciate a bloody mary. If there's no time, I'm happy to wait until we're in the air." IME, FAs--like everyone in a service industry--respond positively to empathy & being treated like fellow human beings.