I think one of the reasons the Kindles lost speakers, and therefore the TTS feature, was that TTS was not good at all, thus many people were not that sad to see this feature go away. With Audible you get a real person who can inflect the proper tones, emotions, pauses, et cetera into the text being read, not to mention actually use proper pronunciation. With TTS you get a lot of garbage. No doubt TTS has improved and will continue to do so, but it will never come close to a real person, especially a trained voice actor, reading the book to you.

BTW, at Xmas I went over to a friend's house and they had Echo. I was not impressed. It had great difficulty interpreting what anyone said, even the owner of the device. My friend had to continually go right above it and nearly yell commands into it and even then Alexa acted like a dumb blonde quite often. His wife laughed, pulled out her iPhone and demonstrated that Siri worked a lot better than Echo/Alexa. No way I would pay $200 USD for that junk. Having purchased the useless FireTV stick last year when it was introduced, I'm not at all surprised at how bad Echo is.