Basically brakes are cheaper, lighter, less complicated and more reliable than thrust reversers. Reversers only really work well at higher speeds and I don't think 100 kts counts (do these things really come in so fast?). Another thing to think about is the possibility of FOD damage. A proper reverser would pick up various bits rubbish which would either damage the airframe and/or the engine by way of re-ingestion. When operating into small airports, I would suggest that the chance of having moveable FOD in the braking zone would be quite high.