Seems like a good question for chatGPT:

Phones typically come with SMS delivery reports turned off by default for several reasons:

User Experience: Enabling delivery reports for every SMS can clutter the messaging interface and make it more complicated for users, especially those who are not familiar with the feature. Keeping it turned off by default ensures a cleaner and simpler user experience.

Privacy: Some users may be concerned about their privacy, and enabling delivery reports can reveal when they read a message. By defaulting to off, phone manufacturers respect users' privacy choices.

Network Overhead: Sending delivery reports consumes a small amount of network resources. When enabled for all messages, this can add up and potentially lead to increased network traffic. By defaulting to off, network operators can manage their resources more efficiently.

Compatibility: SMS delivery reports may not be supported by all carriers or may work differently on different networks. Keeping them off by default ensures that users have a consistent experience regardless of the carrier they use.

Simplicity: Many users don't need or want delivery reports for every message they send. By keeping the feature turned off by default, phone manufacturers reduce the complexity of messaging settings.

Users who want to enable SMS delivery reports can usually do so through their phone's messaging settings. This allows for a more customized experience based on individual preferences.