Given the gaps in the Chitauri's level of technology, Luke really didn't dare use their ships for space travel – one mishap, and the ship would be destroyed.
On the other hand, the Dark Elves' battleships could at least be considered second- or third-rate in the universe, and could ensure basic safety.
Even if they couldn't beat the ships of other races in a battle, they could still escape with their first-rate stealth system.
For Luke, who had never been competitive, there was nothing better than being good at running.
Once he put together an Infinity Glove, he would be able to come and go freely in the universe.
At that time, the Bat Squad would be able to add space travel to their employee benefits. For example, taking Selina to space to look at the stars was a great idea.