Steganographic communication as a substitute for encrypted text is a baffling misinterpretation of the reason for encryption in a chat program. The use cases and potential userbase barely overlap at all.

I don’t want my conversations with my mother to be public. But we are not going to communicate in secret messages hidden in images as if we are espionage agents, and most assuredly 98% of the public will not, either. Not to mention that steganography has a security by obscurity aspect - the more you raise knowledge that textual messages may be concealed in images, and present a common mechanism for doing so, the less effective it is for escaping scrutiny.

Also, I’d note for your points that stegonography has no ‘storage capacity’. That’s a characteristic of the underlying medium. It is not a standalone communication system - if I’m sending secret spy image messages to my tow truck company instead of normal text messages, the storage is foremost limited by the text message system.