Is this a plot hole or plot device?

[weirdsoup]

In Alien, after Brett and Dallas are both killed, Lambert suggests abandoning ship. This idea is shot down as the Nostromo's lifeboat cannot support 4 people so if they abandon ship, one person would have to remain behind.

Now, the original crew compliment is 7, so what kind of ship would have a lifeboat that could not carry the full crew? Or, if the lifeboats are of such a small size, have enough lifeboats to carry the crew to safety?

 

[Asita]

What kind of ship would have a lifeboat that couldn't carry the full crew? The RMS Titanic comes to mind[footnote]The ship had enough lifeboats for 1178 passengers. Its maiden voyage boasted a roster of 2224[/footnote]. It's damn stupid not to have enough lifeboat capacity to ensure everyone's safety, but...well human stupidity is far from unheard of.