I think logistics and risk the main reasons. On average you can expect the jackpot to be split 3-4 ways, and the lump sum payout will only be ~900M. I'm not s

I think logistics and risk the main reasons. On average you can expect the jackpot to be split 3-4 ways, and the lump sum payout will only be ~900M. I'm not sure what the other prizes add up to, but obviously they're going to be significantly less than the jackpot. So given that it would cost almost $600M to buy all the combinations, it is very possible that you could end up with a loss in the tens of millions, if not more. It's not the most likely result, but it would certainly be a consideration. The bigger issue though is how much it would cost to buy and redeem ~300 million tickets. Since you're choosing your numbers, someone is going to have to physically type in each set of numbers at sale. So at a minimum it's going to take like 5 seconds per set just to produce them. Or about 70 years, working continuously for 16 hours a day. Obviously you wouldn't do it all yourself, but even assuming retailers were willing to just continuously produce tickets for you all waking hours, you would need 4000 people working in parallel, 16 hours a day, to get the tickets printed in under a week. And that's just the time to physically type in the numbers. They're also each going to need to store and transport the thousands of tickets. Then you have to redeem them, a process which would likely take longer. So as a rough estimate, say 8000 person-days (8-hour days) overall. Plus overhead for bookkeeping, management, etc. Even so, that would only cost on the order of single millions; a rounding error compared to the jackpot. But can you even find thousands of people willing and able to do this job? They would have to be relatively trustworthy as well. Given the risk, no one is going to lend you the money to do this. So you would need access to half a billion dollars. I imagine most people with those resources have better things to do with their time. (Although if the draw were in a few months, maybe Donald Trump would have a go.)