Using CDN path instead of putting file on your server may not affect developer while developing website. But, it will influence your user to interact while using your product. There are many libraries available in the market. There are some popular large libraries like jQuery, etc available which can be used by downloading and putting them on your server or by adding the CDN path directly. But, remember that using a CDN path is a better approach than keeping that downloaded file on your server. Because, when users browse a website the library is cached on their mobiles and laptops. So, if you are using CDN path on your website then the cached file will act as a catalyst and make the website load faster for the user.
Hope, this will help you to resolve your query.