Add .dropboxignore directory to exclude folders without using selective sync

Why won't Dropbox add a feature where you could automatically ignore files by name? I realize that this is a little bit of a niche feature, probably only needed by power users, but it would clearly be trivial to implement, and I've seen many users asking for this feature.

https://twitter.com/stormchild/status/453914697536794624
https://github.com/tkonolige/dbignore
http://superuser.com/questions/731583/can-i-specify-certain-files-for-dropbox-to-ignore
http://webapps.stackexchange.com/questions/35474/does-dropbox-or-any-other-similar-solution-ignore-files-based-on-regexp
http://www.quora.com/Why-wont-Dropbox-add-option-to-exclude-files-by-filetype-extension
https://www.dropboxforum.com/hc/communities/public/questions/201289669-Ignore-folder-without-selective-sync-

You get the idea, several pages of Google results with people asking for a feature that would take probably less than a week for an engineer to implement.