I'm reading a lot of reasons here, particularly by @PinkElephant for not implementing a simple request. I'm a consultant and every time a client asks me, "Ron, can you..." My answer is yes even when I don't know how to do it. I learn and I meet my customers needs, then they think I'm a hero because so many people they asked before they asked me, only gave them reasons why they couldn't do it.
Every few seconds wasted adds up to minutes, and multiplied by numerous readers a note is shared with in an organization adds up to hours wasted scrolling for information that could have been one tap away in a table of contents at the top of the page, even if the content is only a dozen sections each containing limited but important information.
As a developer myself I know this can be coded by one person within a week, therefore I'll go a step further and ask Evernote to please also include self-updating table of contents that can be inserted wherever desired. Really want to be creative, include the ability to select a first and last anchor, then automatically include all anchors in between whenever they're created.
No need to reply with speculation as to why established document tools can't be coded, as silence is preferable to unbelievable excuses. Thank you GreenElephant. 😊