A great advantage of bipolar transistors (and Darlingtons) is their interchangeability. You need only to match (or exceed) current and voltage rating of the original part and you have a good chance the circuit will work.
With MOSFET you can get better performance if you know what you are doing. But there are hundreds of MOSFETs and there is little chance to have (or be able to source easily) exactly the same part as the random guy from internet and there are much more characteristics that may be important: Gate voltage for turn on, on resistance, Gate capacitance etc.
When you do a beginner set you may add a TIP120 and hope it will work in nearly any circuit that wants a Darlington. I don't think there is a "universal MOSFET."
When you do a tutorial you use a Darlington because when a noob uses another it should work too. Using MOSFET will screw the noob.