I am a millenial, and the coffee thing is a red herring. In my village it used to be the norm for a lot of men to go to the pub a few times a week, the women would perhaps join them on a Sunday afternoon with a sherry. It was all very civilised, nobody getting hammered but it was definitely a weekly thing. Also things like the cinema were much cheaper. There was one in the village - now it's 20 miles away and costs a fortune. When I meet up with my friends, we go for coffee - it's warm, pleasant, we can chat, there's WiFi - or we go to each other's houses, cook for each other and play board games. To an older person, they probably just see yet another group of young women purchasing massive frothy wasteful coffees, but whereas the older generation in my village went to the pub at least once a week, we are lucky to get a meet up at the coffee shop once a month.
Past university, nobody does much drinking or partying. One small drink is going to be £3 at an absolute bare minimum. Then there's taxis. It's all too expensive, and what do you get at the end of it? A hangover.
I can only speak for the people I know, but yes we are careful with our health, there's a feeling that all the social safety nets that were once there are going to disappear by the time we need them.
Most of us have degrees, but have retrained quite a few times to move into different industries /follow the money. Most of us have just bought our first houses or are going to. Sometimes that means travelling to the other side of the country to luce live. Everything is in a state of flux at the minute, the sands are shifting and we are trying to make things secure for ourselves. We know we're going to be the ones cleaning up Brexit in years to come, even though few of us voted for it.
The other trend I've noticed is people getting married and engaged quite young, early to mid twenties. Our parents all got married in their thirties so they actually quite shocked. However these couples aren't talking about children, it's very much about personal development and being part of a team.
I'm the first to have children in my friendship group, I had DD very young, and I think I'll be the only one for quite some time. I think there'll be a massive fall in birth rates thanks to the millenials, partly through choice and partly through necessity