Don't start getting hmphy about it. If Alton opened, you'd have pretty much no coasters. B&M's (anyone who visited Thorpe back in the February openings will know this), have a required minimum temperature to operate. Typically around 4-8 degrees, considering today was -1, you're going to struggle. Secondly, you're guaranteed to valley a coaster when it faces standing snow on the running rail. Think about the wheel assembly; it'll just fill the thing up and add super friction to the train; roller coasters are not fitted with snow plows!
Parks will of course have to consider guest safety, operational abilities etc, but there is also the added question of who in the right mind would venture out into a foot of snow (as is the case at my house in Leeds), to go to a theme park, to get flung around at temperatures probably not far from -10 with windchill considered?
It's full expected and understandable! Also for those living near lightwater claiming lack of snow; it's VERY localised. I work in York, where it's bare, and live in Leeds, where I had to dig my car out this morning - and have seen all varieties of snow cover in between!