Why do I seem to get fewer seasonal rewards than other players?

If you are talking about the Marvelous prizes that only come in the pink star boxes, it all depends on luck and the number of pink star boxes that you open. Many players save their pink boxes (don't open them) so they many more tries to get the Marvelous prizes. The odds are 1 in 10 pink star boxes, so you should expect to open around 20 of them to get the 2 prizes in each set.

As for the other items in the seasonal set, players just need to have coins and diamonds, which can come from playing often or from purchasing with real money. Being in an active lounge club can help with energy and currency.