VHDL, Verilog HDL are basically used to program FPGA and CPLD. Which is used to generate customized ics for specific purposes.
This ics used to interface with various other real time hardwares and peripherals which may include interfaces of different communication protocols like UART, I2C, SPI, MISO, TWI etc. And that is the skill which companies demands in an employer.
By learning VHDL you just learn how to speak.
By learning this protocol you learn how to talk with Father, Mother, Teacher, Elders, Police, Client, Vendor etc.