At least the Cypress tools are freely available and well documented. I have built probably 7-10 products using the PSoC, the tools worked well, resulting firmware solid. Don’t know why you would use Cypress as your example?
Because you can't not use their tools. The register TRM is deficient on some details of the UDB structure like routing, which is essentially mandatory for use the part. (You can technically program the part using only hard peripherals and GPIOs, but that leaves you with a crippled microcontroller.)
