Bitrix Framework is supplied with a huge variety of perfectly tested, secure and high-performance components ("News", "Menu", "Sitemap" and hundreds of others). The standard components is a simplest way to reduce the project development time and costs because all that is to be done is to fit them to the project specifications.
However, there still may occur a situation when no existing component is capable of performing a required function and a custom solution is to be developed. When creating your custom components, use the standard ones as an example of user interface, public section accessibility, performance and security.
On a large scale, a web project can be envisaged as a set of web pages containing standard and/or custom components.
For example, if a customized "bitrix:news" component is used to render the "Details" list, the component name and settings should reflect the purpose: for example, the "News per page" parameter should be hidden.