We make a similar product to Heroku: Continuous Integration as a service (https://circleci.com). I'm amazed at how many developers think their time is free.
"I can just set up Jenkins" is the CI equivalent of the behaviour the OP rants against. And you're right, if your time is free. But it isn't free, and just like Heroku handles your security, scalability and lets you get back to work, so too does hosted CI handle machine setup, test speed, optimization and parallelization, without having to manage it all yourself.
Long story short, developers significantly undervalue their time (and sometimes their bosses do too).
"I can just set up Jenkins" is the CI equivalent of the behaviour the OP rants against. And you're right, if your time is free. But it isn't free, and just like Heroku handles your security, scalability and lets you get back to work, so too does hosted CI handle machine setup, test speed, optimization and parallelization, without having to manage it all yourself.
Long story short, developers significantly undervalue their time (and sometimes their bosses do too).