Enabling MMS on an iPhone is important because it allows users to send multimedia-enriched text messages, which can be embedded with metadata such as images, titles, and subtitles, making them easier to understand at a glance. This feature enables users to send rich and meaningful messages to the largest number of people possible, including those who don't use iMessage. To enable MMS on an iPhone, users need to go through their settings menu, toggle on the MMS messaging option, which is usually located in the SMS/MMS section, and may require disabling iMessage if the carrier doesn't support it. By enabling MMS, users can unlock a more universal and effective way of communicating with their friends, family, and potential customers.