Because a resource is plentify does not mean it should be used wastfully. It means that you should adjust your priorities when optimizing for that resource. Conflating non-optimization with wastful practices is an error.

Ah yes, the 2000s... The decade that gave us Windows Vista managed languages like Java and C#. When RAM and disk were cheap, and code ran like shit because next week's computer will be faster than today's computer. With the explosion of mobile devices, I'm glad we're worrying about system resources again.

Any small improvement helps even a little towards:

1. Battery life.

2. More RAM for the applications you want to run - an OS should be as unnoticeable as possible, including when it comes to resource consumption.

Worrying about RAM consumption is important when your OS is going to run on devices other desktop and notebook computers, such as tablets.