What you should know is that there are benefits to waiving your right to view your letter of recommendation (i.e. opting not to view the LOR), versus receiving an "unwaived" copy of your LOR.
The reason why it is important to waive your right to view an LoR is because it adds merit to the LoR and allows the LoR author to be as honest as possible about their evaluation. If you are applying to the US residency match, then this will be especially important, as program directors will be able to see in ERAS whether or not you selected to waive your right to view the LOR or not. This can be an important factor in how they interpret the strength and authenticity of the recommendations.
Program directors may also interpret waiving your right to view the LOR as a sign of trust and professionalism, indicating that you are confident in the strength of your letters and that you trust your recommenders to provide an honest evaluation of your qualifications.
In addition, it is a professional norm to keep letters of recommendation confidential. Adhering to this norm can demonstrate that you understand and respect professional standards.
In ERAS, there's actually an option where applicants can either click to view the LoR or waive their right to view it.
Ultimately it is your decision if you prefer to view a copy of your LOR, or if you prefer to waive your right to view it. However, we wanted to make sure that you were informed about the customs/conventions as you discuss your LOR request with your preceptor.