What I want to know (asked it before) is why the inner arm of the FC‡ seats dont lift up
Slight delay in me noticing this topic, but I can only think of two reasons why they don't:
1) Moving parts equate to higher maintenance costs - as most people would prefer the armrests down and you don't need to have the inner one up in order to get into the seat it was probably just a decision based on economy.
2) In first class over time I'm sure it would damage or lessen the life of the curtains, as when moved it would interfere with their natural position.
Both reasons are hardly going to bankrupt the company, but small things like that do make a difference over time.