Hi Fang Li,
the reason behind is that you don't have to use additional programmers for each product or device your are manufacturing/testing.
We use the official JTAG Controller from (www.jtag.com). Even the NXP files were checked with their tools for their provided BSDL files. So why not supporting programming as well?
-- Device: K61 120MHz and 150MHz in 144BGA package
-- Package Type: K61_256BGA_17x17
--
-- This BSDL has been validated for syntax and semantics compliance to
-- IEEE 1149.1 using the JTAG Technologies CHKBSDL version 1.0.2.4.
There are so many different Microcontrollers/CPU/FPGA/CPLD etc. Imagine you use a test station where you have to put 15 USB Programmers inside and install 15 different Tools to program your stuff.
Some of them can't be automated due to missing CLI support, so you still have to click buttons.
Altera(Intel)/Microsemi or Xilinx/Lattice programming tools always provide functions to convert their files in the equivalent standardized SVF/JEDEC/STAPL format.
Regards
Jochen