Same here about the size. I think Nero Burning ROM 5 use to be a ~15MB download on its own and the extras such as Nero Vision and In-CD could be downloaded separately so you just downloaded what you were interested in installing/using. The current 293MB size is definitely quite large, especially for anyone on a satellite, 3G or RADSL connection which typically have a tight cap or very limited speed.
I think the reason they went the multimedia suite route is due to most of the basic burning functionality now built into Vista & 7. For example, Windows 7 has built-in data/audio CD burning, ISO image burning and packet writing support (even if rather late now), with the only things left specific to Nero Burning ROM being the advanced features such as disc file system options and the creation of bootable discs.