With a business name, you can:
1) Open a checking account in your business name. Deposit and withdraw money.
2) Open a business credit card to subscribe to data feeds, etc. Make it easier to report tax deductions.
3) Pass out business cards with your business name, just for fun.
4) All your trading statements are in your business name. This makes it easier to demonstrate to other financial entities that you are generating income. For example, if you want to get a debt consolidation loan from a bank, you may need to demonstrate your ability to generate income. Of course, you can do it just as easily if the account was in your own name. Yet, a business name gives it an "appearance" of a serious enterprise and not some back-alley part-time endeavor.
5) Just plain vanity. Some people like to say, "I have my own business and I trade in my PJs".
MGB