It may be necessary to link to specific destinations as a result of regulations or best practice governing the Site. Using the correct anchor text may not be controlled but is still important, especially if YMYL governs the Site.
Google uses authority links as a way to contextualise your content. It attributes authority to your page by understanding the context by which you link to authority sites. For example, if you were writing a piece on financial management and you linked to a related resource on Money Saving Expert (MSE), then Google would see their page authority as a vindication of your content, assuming your content sentiment matches the MSE pages. As a guide, a 2k-3k word article should contain between 3 and 5 authority links.
Ensuring that external links are in good working order is important as Google interprets broken links, looping links, protocol changes and redirects as a poor user experience.