Why is most software lacking important functionalities?

And why it often doesn't get addressed even though clearly many people need that? What can I try to do myself to bring change?

A few examples:

    1. No full text search in (Firefox) bookmarks without turning to extensions or external apps¹.

    2. No way to export a chat log in Signal without turning to external tools¹.

    3. No way for both mobile and desktop email clients to have customized replies (do it the Markdown way instead of the "On date x user y said ...").

    3.1 No cross platform way to have threaded emails. On desktop there are many possibilities while on mobile (Android) k-9 email comes the closest, though it's listed rather than threaded, the way it is on Thunderbird or Gmail website.

¹It adds a dependency to maintain and extra effort to the workflow. It also breaks interoperability between platforms. We're talking about basic functionalities that should be built-in so in my opinion it makes even less sense to outsource it.