They are doing this to iconic characters because it seems no one can create new iconic characters! The last iconic character created was Wolverine and after that, little or nothing, kind of sad.
It isn't like new characters haven't been introduced. They've thrown loads out to the audience, some of them quite good. The new Ms Marvel seems to be gaining some traction...
One major reason why they creating new icons is difficult is that print comics are kinda dyin'. The new characters don't get exposure to the masses on the newsstands nearly as much as they used to, making it difficult for a character to break out into broader appeal.
Luckily, there are already a ton of iconic characters that the market like - so it works well to slightly alter existing icons. Superheroes are modern mythology, and they change with retelling and the times, and that's okay.