Another point to remember is that back then people had no way of preserving juice. They had no preservatives or other modern processes to keep grape juice from fermenting. So once they harvested the grapes for the year and stored the juice in skins, the fermentation process naturally began. If you put juice in a container and leave it alone for a few months what do you get? Fermented, alcoholic wine. That’s what you get.
The passover feast occurred 6-7 months after the grape harvest. By then the grape juice was surely a nice shiraz, or a pinot (ok…I’m not sure how nice it was). So it would have been impossible to not have alcoholic wine for the passover and really for any occasion during the large part of any year.
Read the rest here.