Traditional Art

Regarding your Robert Engel from previously, there's a whole load of artists historically, who have virtually no information about them. If they weren't famous whilst alive, who would bother to write down a biography at the time? Afterwards, you're left with researching records from census, school, sales, newspapers, possible living relatives etc.

A lot of museums and galleries with permanent collections have 3 to 50 times as much stuff in stores as is on display. You're not allowed to get rid of anything, but any year, you might receive another truck-load of badly labelled and badly maintained artworks from some rich bloke's private collection, or someone's tax write-off. You'd have to choose which ones get processed or researched first (after the existing backlog). Sometimes the information just isn't there though - that's why you get all those works that just get labelled "Unknown Man with a blue hat, likely Dutch School, circa 1650s".

I think the information and documentation of such things is actually getting better, compared to pre-internet, certainly - but yeah, some people will have no information, and some will have information, but it's still in a paper folder, waiting for someone to type it up :)