Quite simply, they don’t. Ship owners usually prefer time charters, as they ensure that their ship is guaranteed to be chartered for a longer period, generating income throughout.
Voyage charters are short, meaning the ship owner must continually find new charterers to lease the vessel to – something that isn’t always possible. When a new charterer can’t be found, the ship owner loses money.
Please note that charterers are required to take out insurance for both types of charter, to cover them against damage, injury, marine salvage, and more.