By supporting de jure standards (vs. Google projects which hope to become de facto standards), Apple gets a 3rd-party ecosystem for use cases where it wants one. Examples include USB, Wi-Fi, MPEG-4, Thunderbolt/USB4, web standards, etc. In many cases, Apple is an active participant in the standards process of de jure standards which are important to their business objectives.
When de facto standards develop enough momentum to have customer value on their own or as part of other de jure standards, Apple will support them at the OS or app level. Examples include MP3, VP9, Opus, VST3, etc.