I believe (when it comes to Notables especially but family as well) that there are two phases that can often be separated by large periods of time (even though there are exceptions). - Profile Initial Entry - and - Profile Improvement.
It's tough, when you're first starting out, as you want to see your tree emerge, fully formed, and there is a period where profiles are either GEDCOM created or quickly entered one after the other in a rush to populate the tree. I get that. It's exciting to see new levels pop up from your tree and there is a sense of satisfaction looking at a tree view and knowing that you have profiles in each of the spots.
However, I get your point - when do we return to improve said profiles that may have been quickly generated with no sources, not linked to the global tree, and whose story has truly yet to be told (no biography)? And how do we keep track of all these profiles? Even more interesting, with Notables at least, there's always a push to churn out another Notable into the tree (being famous in some way, there's always interest in so-and-so who I saw on TV, film, heard about in history class, etc.). And unfortunately, many of them do get created with a name, a few dates, and a wikipedia link.
I've been treating this like the whole eating the elephant principle. I can only improve one profile at a time, and I start with family and sources and hope to one day return to do more. I try never to leave one behind that doesn't have at least one primary source, has the family identified and profiles entered including father, mother, siblings, spouses, and children. It's time consuming - yes - but it's so very important. We never manage to get these strays connected to the tree or sources established unless we make a concerted effort to keep improving our profiles. I think the more profiles we can establish that separate us from a simple wikipedia entry where we have established family links, true genealogical research being done, clear links to the global tree - then I feel I can sit back and feel that we've accomplished something great. And it starts with one profile at a time.