This question already has an answer here:
In the 1950s and in the early 1960s, jets were mostly available as fighter/military or big, long haul aircraft. Regional aviation was based primarily on piston aircraft that could operate in smaller airports. When planes like the Boeing 727 and 737, Douglas DC-9 and Hawker Siddeley Trident came out, they finally brought the jet era to the regional aviation. But still, they were loud and inefficient. That's where the turboprops come in: they perform better than pistons and are suitable for small airports; they don't go as fast as jets, but are usually cheaper to maintain.
Given all that, most regional airlines started to use turboprops for their city links.
In the recent years, however, jet engines are getting quieter, more efficient and powerful. Embraer's Regional Jets and E-jets are out there; more recently, we've seen Bombardier releasing their CSeries and Embraer selling the first E2 units. Even though these planes are highly efficient, fast and suitable for short runways, airlines from countries like Brazil, Indonesia and India are still using turboprops as almost the entirety of their regional fleets. The development of modern planes like the ATR72-600 and the Bombardier Q400 shows how high the interest from airlines is.
The question is, what could be the cause of such preference? Why don't airlines prefer regional jets over turboprops, given their efficiency and speed and considering the tendency people have to "fear" propeller planes as old and untrustworthy?
Speaking of numbers, what would be financially better for a company: flying an ATR/Dash 8 or a modern jet like the E2/CSeries?