JK flip-flop: What is the difference between clear and J=0, K=1, rising clock?
asynchronous vs. synchronous

asynchronous is easy for resetting the flip flop at power up. It does not require a clock to reset the flip flop.

synchronous is easy for changing the output to 0 during normal operation, it requires a clock to propagate to the output.

I could imagine if you want to build a counter, you want an easy way to reset all outputs to 0 at power up. The reset pin is ideal for that, because at power up without reset the outputs will be undefined/random. With the reset pin a power on reset doesn't require the input logic gates to get more complex.