Maybe bending relativity can have negative mental effects that aren't enjoyable to experience. Aliens Nightmare Asylum says that, did anyone see Pandorum? Also, if human space travel is based on Predator space travel, then it's likely that some of their ships have hypersleep capsules. Maybe they're only used on certain occasions. Wolf probably decided to bend relativity cause it was an emergency, otherwise he'd have used a hypersleep capsule or something.