I am sure that there are many reasons, but here are just a few on my top 5 list…
1. You will be working in a true building model environment (one model, one file), not many files with xrefs and such like ADT.
2. Divide your work among users via Worksets. Even though you are all working in one big file, you can divide the work up among the users.
3. All building views are updated no matter where you make the change. You can work effectively in any view.
4. No need to worry about Layer Names