The winnings themselves aren't taxable, but the whole rest of the process is. Say I buy a 15 dollar lotto-max ticket and 1 million tickets are sold. That's a total pot of $15,000,000.00.
Out of that 15 mil pot, 5to8% of that is going to the retailer, 10to15% is going to the lotto company, and then 15to20% of that is going to the AGLC, then around 20% is going to the CGA. Around a third of that pot is going straight to the government; the lottery winnings pot will end up around 7.5 million or so.
If the winnings were taxable, you're taking home 12 million, then paying 35% of that straight to the government, and then taking around 7.5 million to the bank. Lotteries are certainly taxed, you just don't see it as the winner. You don't think the Canadian government just decided to let around a billion a year in personal incomes go un-taxed, did ya? In fact this method is actually safer for the government; less likely Joe Smoe gets a 12 mil payday, blows 10 million of it instantly without any fiscal planning, and now owes the government a 35% tax bill of 4 million that he'll never be able to sniff at making in the rest of his life. This obviously leaves the Gov't holding the bag, but also requires them to prosecute the tax evasion to maintain their authority. Not to mention, all the money going into the pot is post tax from your paycheck regardless.
Even 50/50's are taxed slightly this manner, although at a significantly discounted rate given the small scale and general charitable intent. You certainly require permits to run 50/50 draws just like all gambling and gaming's of any kind; while the pot from the 50/50 itself does not get taxed, whomever is applying for the licence to run the draw pays for a permit based on a reasonably expected ticket sale value; it typically ends up looking more like 50/40to45/5to10. The Tax Man always gets his cut, which is (imo) good: educate them kids, keep the potentially dirty industry well regulated and clean, build us all infrastructure, provide me and those I care about who can't care for themselves with social programs and a safety net.