A more realistic somewhat rational reason to buy lottery tickets would be when the gains of the lottery company are used to fund charitable projects and someone would reason that buying a lottery ticket increases the jackpot and thereby makes the lottery ticket more attractive to a lot of irrational people and thus increase the gains for the charity.

The fraction is really not very large. Camelot (the lottery operator in the UK) has in fact been specifically enjoined from stating or implying that buying a lottery ticket meaningfully contributes to charity.