I can empathize with an organization interested in motivating its employees over the long term. SPAs, GraphQL, and these other non-essentials are intrinsically rewarding. They give the creators a sense of agency. This motivates people to give their work their best effort. From AirBnB perspective, as long as the value created by these projects doesn't exceed their costs (a quasi-NPV), why not continue them?

The next chapter of intrinsically rewarding work will involve simplifying the complex. Trimming the fat. Reinventing the Zen of Python. Most importantly, it will be glorious.