Why do more people recruit the first mate than the second mate?

There are few sailors. There is a temporary shortage of seafarers in the international shipping market, and the epidemic situation is relatively stable. Even in some countries, the epidemic situation has been normalized, so trade has gradually become active. Compared with the initial stage of the epidemic, trade has also been greatly improved, so greater ship capacity is needed to facilitate the transportation of goods. There are more ships, so more crew are needed.