I joined a day tour to Yarra Valley when I visited Melbourne, Australia, a few years ago. It included a visit to a winery for wine tasting. On our way there a fellow passenger asked the driver whether there was a day tour that covered purely the wineries in the area. The driver smiled and replied the agency used to have a day tour like that but later some passengers got a little difficult to handle after some wine tasting, so the agency removed that day tour and limited the number of winery visits in their other day tours in the area. He did not elaborate the part on difficult passengers but I guess either some got drunk and became abusive, or fell into a deep sleep and could not wake up after the tour ended.
It has been a few years since that visit so I wonder whether the agency has revived that day tour after a review of market demand.