[quote=@Lord Wraith]
Media such as the MCU Movie Captain America: The First Avenger have displayed an updated take with Bucky being Steve's friend growing up and an alley in war without having to dress in a costume. [/quote]

They used even old Bucky to justify why no-one in the Avengers have a sidekick (Unless you count War-Machine as it looks like he's going to be very sidekick in Civil War. Same as Falcon).

I think Sidekicks can still be an important part to the story. Though they are certainly becoming out-dated. There's an element of the fact that the Hero has to look after them all the time that's become less and less popular with teenage heroes/sidekicks coming into their own element rather than in the shadows of whoever started that legacy.  

They provide a very important part of story-telling but it doesn't work for everyone. DC as it is seems far more fond of adding legacies and sidekicks than Marvel however.

[sub]Superman even has a super powered freaking dog.[/sub]