My original post said that you don't have to have "trader status" to carry forward losses. All investors have that opportunity. I am not sure where there was a communication gap but it's resolved now.
Totally false or more appropriately: not even relevant to what we were just taking about with carry forward losses. Your implication is that without trader status one cannot use carry forward losses against future gains which simply isn't the case.
If the OP plans on being a pattern day trader with enough transactions, then he's trading as a business. One of the biggest advantages to consider is the MTM election, which eliminates the "wash sale" rule.
Primarily, There are 3 US tax advantages when qualified with "trader tax status" versus "investor tax status". 1) No limit on capital loss versus MAXIMUM of 3k PER TAX YEAR capital loss w/carry forward of remainder usable at a maximum of 3K PER TAX YEAR with investor tax status. 2) No wash sale reporting. 3) Ability to fund and provide retirement and health benefits, both which require earned income. Capital gains with investor status is not earned income. There are several other US tax advantages available with trader tax status. There are also drawbacks, the largest being SE tax. Now, if you want to think none of that, especially item #1, is "relevant" or false with regard to carry forward losses, or inappropriate for a trader tax status discussion, then we should all just answer the OP's question... Do you need a business entity to qualify for trader tax status? No.
SE tax does not apply to a sole proprietor with trader tax status. But then you can't fund a retirement plan.
Gains and losses from selling securities from being a trader are not subject to self-employment tax regardless of whether structured as an individual or entity. If you structure and conduct your business appropriately as an entity you can legally avoid tax on a lot of the profits. This can be a huge benefit... for details ask your CPA how this can be done. If your CPA doesn't give you ways to save big, start looking for a good tax attorney. Corporate tax attorneys that know their profession know these details.