While your statement of purpose will underline who you are and what you want, your letter of recommendation will substantiate those claims. It serves as a validation of everything you have said in your application, providing the admission committees a third-person, realistic view of your portfolio.
The LOR would talk about your strengths, interests, and other aspects to increase your chances of admission.
A letter of recommendation from a renowned personality can add a lot more weight comparatively. However, many top universities focus on relevancy above all. For instance, if you’re applying for an Economics major, your LOR coming from someone who has established experience in this topic would hold a higher value than, say, a celebrity.