Honestly it bugs me a bit that I don't know the right way to model it - because so often people will slate it for having a terrible expected return (E[X]), but.. some very high percentage of us here could play every single week without noticing it (negligible downside), and yet winning however slim the chance would be somewhat life changing - even if it wouldn't make you quit work it'd be a nice windfall.
I suppose you can just view it as a microcap, very high risk investment.
I don't play, fwiw. I do have Premium Bonds, a lotteryish government scheme in the UK where you keep the invested amount and it can't go down (other than in real terms) but has a shot at winning various amounts each month up to the maximum of £1M. That's a lot easier to justify to myself, but I do wonder if it's a bit too easy to dogmatically hate on the lottery.