Because their mission isn't to generate income like a traditional business. But if the income went back to the foundations, like Python Foundation, I think that would make sense.
But income can be also used to help finance their main mission. Obviously they seem to operate fine without strong reasons to expand revenue streams, but I feel like they ignore an opportunity to create improvements for just about everyone.
Anaconda gives a healthy amount to open source, either by donations to foundations like NumFOCUS or paying salaries of contributors. Is that what you're looking for?