Cost: one speaker and tubes was probably cheaper than 200.
Weight: old headphones were chunky, see above.
Comfort: not wearing giant chunky headphones you weren't accustomed to might have been preferable
Breakability: pneumatic headphones were harder to break, cheaper to replace
Stealability: passengers would have no reason to steal the headphones, and if they did it was cheap to replace.
All of these go away as proper headphones get increasingly small and cheap.