what would you do as a parent? you know that people dont really get the message unless you do something drastic. i doubt they'd take away your entire ski season but they obviously want to do something that hurts you that's going to make you think about it. like if you're losing skiing then it'll be 'oh no i'm never going to do that again skiing is just too important to me'. being grounded is like 'fuck if i care, a week goes by and shits no different'.
parents are just trying to do what they think is best for you, and lets face it, there's really nothing positive that can come of being a burn-out. i'm not saying you are a burn-out, but from their point of view, they certainly fear the worst. wouldn't you? trust me, i've known those kids growing up, and now they're 25, working shitty trades and wishing their parents cared a little more when they started the tailspin.
be thankful you have parents that are trying to do things that make your life better inthe long run. again, smoking weed really isn't that big of a deal, but it's always about the worst case scenario. being a burn-out or a drunk could lead to some bad things later in life, and it's safer to say don't smoke weed ever than to allow it, not care, and have things potentially get worse over time.
it was the same with my parents. drinking was kind of forbidden. they knew i was drinking out with friends when i was young, but it wasn't something they promoted around the house and encouraged people to come over and get bombed. so i grew up not caring so much. when i hit my 20s, yeah, of course i drank a bunch, partied, all that, but i have really had urges to get bombed or felt that it was something that i had to do to have a good time. you know those kids who's parents just dont care and want to be all cool and drink with you too. i have friends like that. everyone does. they grow up feeling like they can do no wrong, and where are they now? probably still partying and drinking like they're 18 at clubs and shit, but they're 25, and when everyone has moved on with their life, theyre stuck with that childlike mentality because they've never been told otherwise. of course, that's not entirely the parents' fault, but it's nice to have a little guidance. shit, remember when your parents forced you to take piano lessons? forced you to sit down and do your times tables? think of how much you appreciate those skills now, because you know how to read music, and can do simple math, quickly, in your head.
sometimes you just need to be forced to do things for your own benefit, as much as you hate it or hate your parents at the time, because then you grow up and think 'god damn, they were right'. good ol parents. gotta make us do shit against our will because they know it's good for us, despite all of the hate they get for it.
anyway, i veered off course a little bit there. point being, appreciate that your parents care. they're not trying to punish you, they're trying to do something that'll get the message through. i highly doubt they'd take away your hobby and an active lifestyle, it's more something they're threatening to make you understand that actions have consequences and you've got to own up to them. if you keep smoking, then they can say 'well i told you you were going to lose skiing, so if smoking weed is more important to you than skiing, so be it. that was your decision'. they're leaving the ball in your court and seeing if you're going to do the responsible thing.