Its low cost and being completely self-contained made the KIM-1 unique among the 6502 computers of the 1970s. It was a small fraction of the cost of an Apple, Pet, Atari etc. which made it practical to build into an embedded controller as if it were just another part.

It did not require an external computer or terminal to use, you could program and run it from the built-in hex keypad. The simple 6502 instruction set did not require an assembler, it was quite practical to write the assembly language program on paper and then hand-assemble it by looking up the hex opcodes -- after a while you remembered the most common ones -- this was actually simpler and faster than dealing with program development tools. It only took a few minutes to key in a couple of hundred bytes, which was sufficient for many control programs -- you were not using the KIM as a personal computer, but as a (much better!) replacement for dozens of TTL chips and IC timers.

You could use it to do real work, build real devices. I built this programmable gas mixer for respiratory physiology experiments:

https://journals.physiology.org/doi/abs/10.1152/jappl.1980.4... Programmable Gas Mixer ..., Journal of Applied Physiology 49(1), 1980.