> Optimizing memory server-side directly translates to cost savings for companies.

Only if those cost savings exceed the cost of development. Optimisation work is usually done by the most experienced, and hence most expensive engineers. It is also possible that the optimisation efforts will fail to produce meaningful results. In my career, I have seen more optimisation efforts fail than succeed.

That's a clever observation and is very true. Development time tho historically was also very expensive hence push for easy to work with dev stacks such as js

There's plenty of incentive if it causes your users to churn.