This is the point I was trying to make in my comments earlier. Typography is a feature. Right now we're seeing Minimum Viable Ebooks. Ship.
What is the incentive for better typography? Most books are like mini-monopolies (over the short term). If the typography of a book sucks and it sucks on all platforms, what is a consumer to do if they want to read the book? Fallback to print? Publishers probably don't mind that. It's true that all things being equal, typography could be a deciding factor for the consumer, but my gut says that in most cases the content is weighted much higher.
I think the platform could benefit from typography. A consumer may choose an iPad over a Kindle if the iPad had a better reputation for typography. But since there is _art_ involved it might not be economical for the platform to pursue it. Which is a better selling point: Our platform has 100 really nice books or our platform has 100,000 books?
No, but this is how the iPod beat every other mp3 player -- it was just undefinably better to use. Typography is one of those features; most people don't think they even notice it, but they do.
Your mom might select a kindle fire if she hears from all her savvy friends and family that the kindle fire delivers a better experience. She may even hear why it does, but she may not care about the why, just that trusted sources inform her it is better.
I believe this is true in general. A few savvy people catch on that a product is better and it becomes a meme that others rely upon for their decisions.
Don't talk about my mom like that! (In all honesty she is not really into savvy/hip people;)
I do not think that there are enogh savvy-typography-valuing-people to induce some market driving meme. If this was the case Word would have died many years ago...
Typography is more art than science.