There are three main benefits to installing the Facebook Pixel. The one that really counts for most businesses is Facebook remarketing. In other words, you can set it so that your web visitors, a very important target audience, see your ads during future Facebook visits.
The second benefit is seeing the analytical and demographic data of website visitors. Given that the near ubiquitous Google Analytics platform already offers this, I don’t see much added benefit here. The third benefit is the ability to track actions taken on your website, in which the visitor’s journey originated on Facebook. This could be beneficial if a business is running a complex orchestra of different Facebook ads, in which it’s important to identify the exact ad that caused certain actions (e.g. sign up for an event). Also, I’m not sure if assigning Facebook code to a website action precludes the tracking by other platforms; for instance the Google Adwords conversion tracking does preclude phone tracking by other platforms, in certain circumstances.
Anyway, for many businesses, it’s worth installing the Facebook Pixel, if only to employ Facebook remarketing.