Unpredictable or random rewards are more addictive than a predictable schedule.
"Battlesuit fragments/souls may or may not be obtained when completing one of the few missions that they are obtained from."
"Most notably, the rewards obtained from daily dungeons are variable. Sometimes the reward for completion can be desirable, other times they can be insignificant and disappointing."
"Whenever the player has an investigator complete an adventure during gameplay, certain items (such as common, unique and spells) are chosen from a pool at random. The only information the player knows ahead of time are the type and quantity (two unique items for completion, for example) of these rewards."
"Chest rewards are "cards" of a random category of song, which when enough are accrued will unlock a song from that category."
"The game has a gatcha (Energy Rewards) that requires playing matches to earn points to use the gatcha machine. Chances of winning a valuable reward are low."