Why is LiFePO4 basically invisible? Because it hasn't lived up to the early hype.
The same was true of some of the earlier lithium ion battery chemistries, but they had the advantage of coming first, and most of their growing pains are behind them. As a result, ongoing R&D is amortized across the huge market for traditional cells, and has been bringing steady progress.
Some things to think about:
* As recently as 2013, commercial LiFePO4 cells had serious capacity fade when charged at elevated, but not unusual, temperatures.
* If you treat other LiIon cells as if they have the energy density of LiFePO4 cells by limiting their operating voltage range, you can get real lifespans that are similar to the promised lifespans of LiFePO4.
* The power delivery capabilities of LiFePO4 aren't really important for most consumer electronics, and for many applications where it may be more important like power tools and electric vehicles, runtime is also an issue, and so energy density is an issue. Once you get enough cells for desirable runtimes, per-cell power delivery is less of an issue.
We'll see what the future holds. I'd say though, that the expectations people have of traditional lithium ion batteries wearing out after a few years is probably more about the average lifetimes of the consumer electronics that most of them went in to. There is going to be huge growth in the coming years in electric vehicles and fixed power storage, both of which have longer lifetimes. Batteries for consumer electronics could be less than half the market in less than 5 years. I expect battery lifetimes will improve rapidly. In fact, they probably already have.