Fixed income fixation? Why is it increasingly popular?

Nothing new. Most people don't realize this, but the bond market has always been far far larger than the stock market. Think about how many houses there are in America, and how many trillions of dollars of mortgages there are -- all that ends up in fixed income. Heck, the US federal government alone has 30 trillion dollars of bonds outstanding. Now add on bonds from all the states, all the counties, all the cities. Plus most corporations (even big tech companies like Apple) issue bonds. The bond market is huge. 

The other thing about fixed income is that they tend to be more profitable for market makers than stocks. Even though the total bond market is far larger than equities, most individual bonds (other than treasuries) are a bit less liquid than most equities, so the bid-ask spread is wider. Also, the value of bonds can be calculated very precisely mathematically, whereas valuing stocks involves more guess-work, so the bond trader often has more informational advantage over counterparties than equity traders do.

 You ever read the book Liar's Poker? You ever hear the line about how he was afraid he'd fail his test and be sent to trading "equities in Dallas"? That's because trading bonds was much more profitable than trading equities. (At least on the sell-side banks. The answer might be different on the buy-side hedge funds)