Party because of marketing efforts
High ball is a drink mainly consisting of whisky and soda mostly served in rather tall and big glass. In Japanese market, consumption of hard liquor, like whisky have been on the constant decline over the last couple of decades while beer and Chu-hi have been continuously gaining popularity. In order to cope with this issue, liquor producer, specially Suntory, a leading Japanese Liquor producer, poured massive adds of high ball on TV. Thanks to those campaign, whisky high ball made a huge come-back in these few years . Chu-hi (Shochu high ball) has long been a popular drink but it is rather a new product with say, 20 years or so history. I think it was introduced in mid 80's to cope with the decline in Shochu demand. So, kind of a same story all the time.