(They do help clubs sell things, taking "7% of income", so they do have a revenue stream, but the money that Slack wants would pay a veritable army of student interns.)
You don't want an entire generation of people who can barely operate the devices that enable and control a huge portion of their lives.
Kids will benefit immensely from being able to logically reason, and will be less afraid to repair or work around shoddy software, even if they never write another line of code in their lives.
Professional programmers dont fear kids taught to code any more than novellists fear kids taught literacy or accountants fear kids with numeracy. If anything, they know personally how important it is to learn these things.