This is not a setup I use, so others may have more specific comments, but for a lot of Drafts users they prefer to keep Drafts as their temporary storage where they gather fleeting thoughts, ideas, tasks, etc., throughout the day - and have another more curated long-term storage system for notes.
In the paper world analogy, Drafts is the inbox on their desk - Obsidian (or other system) their filing cabinet. Some things that hit your inbox end up going back out to someone else’s desk, some to the shredder - and only some to the permanent, organized reference source of the filing cabinet.
People have used Drafts like this for years with different back end storage systems - from Evernote, to files in Dropbox. Obsidian seems to be a new popular choice for this type of reference because of it’s enhanced abilities to cross-reference documents.
(Obsidian people feel free to expand on that or clarify if I am wrong)