What the SIE is for
It is the entry-level exam covering industry fundamentals: products, market structure, regulation, and prohibited practices. Crucially, you can sit it without being sponsored by a firm, which is unusual — most securities exams require an employer to register you first. That makes it the accepted way to demonstrate commitment before you have a job in the industry.
What it does not do
Passing the SIE does not allow you to sell securities, advise clients, or transact. That requires a top-off exam such as the Series 7, and those require a sponsoring firm to register you. The SIE is a prerequisite and a signal, not a licence, and any resource implying otherwise is misleading you about the structure of the industry.
Why regulation is so much of the content
A substantial part of the exam covers rules and prohibited practices — insider trading, churning, misrepresentation, suitability. That weighting reflects the job: the constraints on what you may do and say are not paperwork around the work, they are the work. Candidates who treat that section as memorisation tend to find it the hardest part.