Why is the American TV Drama "Friends" translated into 《老友记》?
The title "Friends/ 老友記" is most likely translated by Hong Kong Cantonese


老友 means 'old friend' 
記 means 'brand' 


老友/ 老友記  is a colloquial Cantonese term that means "old friends" or "good friends"

老友 can also be used as an adjective for "friendly" For example, "無端端同佢咁老友?" (Be so friendly with him for no reason?)


  Using 記 to form a nickname is very common in Hong Kong Cantonese,


The nickname for "香港廉政公署" (Hong Kong Independent Commission Against Corruption) is "廉記" (the 'incorrupt' brand)

The nickname for "有組織罪案及三合會調查科" (Organized Crime and Triad Bureau) is "O 記" ( the 'O' brand)

If a person is named  "陳家強", his common nickname could be "小強" or "老陳" in Mandarin and "強記"  or "阿陳" in Hong Kong Cantonese

"Friends" is a comedy, and the colloquial term 老友記 carries an informal (casual ; relax) tone, which fits the series very well; On the other hand, the literal term "朋友們" sounds too formal, 

Interpret 老友記  as "journal of good friends' would sound too formal for a sitcom