Random Number Generator is random. Lady Luck is fickle. You just got unlucky. Etc, etc. It's a gamble when you open a lockbox. You need to realize that: A. GAMBLE. Cryptic made this quite clear in the FAQ about the lockboxes.

The probability of getting the big prize is very low. I haven't seen a study of this lockbox yet. But if past box probability distributions are the same, the chance of getting a ship is 1 in 200 or 0.5%. Imagine flipping a coin 8 times in a row, and the coin coming up heads ever time (heads 8 time on a row). The odds of getting your ship is slightly better (0.5% vs 0.39%).