Working memory is waaaay more critical than you might think to all levels of functionality. There are many basic tasks, like walking to another room to get something and noticing something minor, like a pen on a table that should be put away, and doing both tasks, that depend on working memory. The same with mentaly reasoning through a complex system. The reason abstractions are so valuable is that they allow for compression of something into working memory.

For me, personally, this is why I often approach things by scaffolding them into relationships with existing structures (mentally) - by integrating with an existing structure, I avoid a sort of fragmentation overload in my working memory.

Anyway, I think it's one of those things you don't really notice until it goes bad somehow.