You are not required to complete the evaluation. However, performing the evaluation will help you stand out by demonstrating that you have the desired skills of an ideal candidate, in addition to increasing your chances of being noticed by other recruiters. Recruiters won't be able to see your score. Recruiters can search for people who have passed specific skill assessments as part of their search parameters and filters.
So, if you're a recruiter, make sure to bring these completed questionnaires to your client's attention. They'll really appreciate having a skills check and their candidates will enjoy a faster and possibly less expensive hiring process. Linkedin is viewed as a trusted site by ranking archives and giant companies. However, there are no measurable criteria for how skill badges impact the hiring rate.
They can be used to give first impressions of human resources, but from a technical point of view, they do not serve to demonstrate a person's technical strength. LinkedIn won't tell you this, but the addition of evaluations is the result of LinkedIn's acquisition of an online testing company, ScoreBeyond.