One gains not needing to learn another language. I know C, I don't know Verilog or VHDL. I know how to debug C, I don't know how to debug Verilog.
If I can write a working C program, why can't I make working hardware?
If I can write a working C program, why can't I make working hardware?
Debugging HDL involves looking at timing waveforms in a simulator.