Staircases take up a lot of space, so why not use them for storage as well. Imagine each step is a box with a hidden drawer in it still allowing for additional storage or home office space beneath the staircase.
Awesome idea if a bedroom is against a hall closet! Never really use the entire hall closet anyway! Save on the clutter and fill uneeded space in the closet to be used for more floor space in the bedroom!