JPEG 2000's approach provides successively finer detail so the entire image can be rendered after only a small percentage of the total data has been received and then it just becomes sharper as data continues to stream in.
If you'd ever watched an interlaced GIF arrive over a slow connection, that's exactly how it looks.
I've watched plenty of GIFs trickle in – over a 1200 bps modem back in the day – and it's not the same. An interlaced GIF displays every other line first, leaving a visible comb pattern between the lines until the rest of the data loads which is visually quite distracting unless the background is transparent or a compatible color with the image content.
Here's what interlacing looks like, with whole areas being empty until the data is received:
With something like JPEG 2000, you have a completely experience because the image renders immediately with less detail and becomes sharper. Using this example from Wikipedia, it'd basically start with the 1:100 frame on the bottom and rerender as data streams in until hitting the final 1:1 quality at the top:
If you'd ever watched an interlaced GIF arrive over a slow connection, that's exactly how it looks.