I use "science" not luck when I'm in it to win it. One of the best courses I took in college was statistics, where you learn the math behind the odds. I do buy certain raffle tags where the cost compared to the odds makes sense.
On the other hand, as some of you mentioned, if I see it more as a "donation" where it benefits wildlife, I'll throw my name in the hat even if it doesn't make sense. One of those for me is for the Montana sheep raffle tag.