Yes, it’s an MMS feature. But iMessage makes it way too easy to “text to email” inadvertently when you start a group chat with some non-iPhone users. MMS sucks but it’s the universal way for iPhone and Android users to communicate without needing everyone to be on the same third-party messaging platform like WhatsApp. In my US-centric personal experience, there is no universally accepted messaging app you can be certain that everyone is on.