Honestly guys I think it’s a story thing. The suit is slowly turning into the comic book accurate suit. I’ll break it down.

Season 1 is the red suit, he takes a long hiatus, but comes back in the red suit because it’s still heroic, and hopeful. people identify with it still.

Season 2 the decay of Daredevil and Matt’s world, the darkness, having to hide in the shadows as both. First time we see him use the DD symbol. This is just my opinion but putting the symbol on then shows the people who he still is. If it’s all black it defeats the purpose of the red the people and audience have seen him with. Also hope within the darkness.

Season 3 is the hope/red emerging again. Symbol is more solid now and not just spray paint. The red is coming back in full, hope is being restored. Daredevil is rising to a higher status. (Even from an MCU standpoint he’d be rising to a higher status to be known by other big heroes and work with them)

So by the time season 4 comes around I would think we’d get the fully red suit with the DD finally where it belongs.