While the system worked in theory, in practice it meant that people were stockpiling event currency on alts, secure in the knowledge that next year they could just unlock the ship once without much effort and then get it on the cheap elsewhere. As a result, the currencies are being changed, but these event prestige ships are being shifted to account-wide unlocks to keep alts in the loop. It’s not an ideal solution for those with lots of currency saved up, but it keeps the ships you’ve earned and also makes sure that people are still taking part in the content.
Star Trek Online is doing something new with its summer event this year by shifting currencies in a big way. This has caused a fair amount of consternation among the playerbase simply because it’s a radical departure, but a posting on the official forums explains the logic. Simply put, it all springs from the fact that the designers knew players wanted to get the rewards on alts, so it was made cheap and easy to redeem the currency for a second ship after you had unlocked it on one character.
Source: Forum posting