I suspect it is because snow storms are fairly rare or at least random and quite a few people do not a) realise they have not done much of any physical exercise for ages b) think shoveling snow is easy, try to do it fast and take too big loads into shovel (which you can with snow, but not with sand). For older people this might mean overexertion and possible seizure, if their cardiovascular health is not well either.

Solution: don’t be a hero. Take breaks. Take smaller shovelfuls. If the first ten shovelfuls are hard, how hard is the 1000th going to be? I live in Finland, are fairly fit and quite strong, but shoveling the car out of thick snow for half an hour is pretty hard work for me. For an older person, it must be double as hard.

Cold weather itself increases the chance of heart attacks. Heat waves get all of the news coverage, but cold weather is the real killer: https://www.wunderground.com/cat6/Which-Kills-More-People-Ex...