I would very much rather come up with a few details at a time about a character during play than worry about a whole life's story all at once.
Sure, I will likely have an immediate, 'reason for adventuring.' which may be something like, "can't cope with civilized society." or, "it beats living on the streets." or "it is a way to give back." which may then lead to questions that are answered in play.
This is one of the player taste spectrums that rgfa called Develop at start/ Develop in play back in the day. Some players write long multi-page backgrounds for the new characters, others are reluctant to write a single short sentence, the vast majority being in the middle somewhere.
I find this peripherally relevant to the topic of this thread as low background pcs can make more work for the referee. Character backgrounds/motivations are the primary vehicle for communicating PC hooks and goals to the referee for adoption or integration into the setting. Often there's some negotiation and editing of backgrounds so they fit the particular gameworld the referee intends to run. A player being unwilling or unable to provide a background in a way throws all the initial work on prepared plot production back to the referee, and means they have to monitor the players with less background more closely to figure out what they seem to like and dislike.
Players produce what they produce as regards backgrounds, I place some pressure on most to produce a little more material than they would by default. (I don't ever ask for less, as that can make players clam up entirely, I just don't guarantee reading mini novella length backgrounds). It is generally possible to get a single sentence or character concept from even the most recalcitrant players, possibly in discussion. Most players will volunteer a little more given time and positive encouragement.
One reason for "ophans with no background or links" is when they have been conditioned by bad referees to expect every NPC linked to their background to be taken hostage or slaughtered for plot purposes. A number of hours play with a new player generally make it clear whether they are worried about bad dm calls or just hack and slash merchants (the other main motivation for a blank slate background). Rewinning the trust of players so they can dare to write backgrounds that don't immediately blow up in their face can be difficult, but it is possible.
A character concept that develops in play can be harder for the referee to negotiate about, as it may develop in ways that don't suit the main plot, the gameworld or the referee's tastes, and IMO it's easier to get a player to modify concepts on paper that have never been played rather than modify an emergent unwritten PC personality.
I have to admit I prefer players who can produce a short relevant PC background with a few personal hooks, goals and quirks, as it makes my referee prep easier.