If you are having free crew fly in, there is no excuse for not having the boat 99% ready (there is always a little "surprise" with boats, however!).
The weather, however, is beyond the skipper's control: Sometimes it is merely good seamanship to wait a day or two, particularly when the crew or the skipper or the boat are not experienced in heavy weather.
But it does seem to me that a lot of people show up as crew not to a situation where the skipper says "we have to buy groceries: do you have any special food needs?", but rather "we have to
paint the bottom...here's your roller, get to work!"
Now, if that is the explicit understanding: "a week's hard work buys you a passage to destination X", that's fine. But it seems that a lot of skippers are looking for free labour and time in return for more free labour while they get to go offshore. Not fine.