As I start to look with more attention to the map of Westeros and compare to real life geography it completely destroys the idea of second sons having no land or even titles (famously a TB argument against Otto and Alicent being some type of gold digger who didn't deserve a King) or bastards sons, like Daemon, should be thankfull to get even a small keep.
I understand George wanted a very simple worldbuilding, as one house = one Castle (but for the Peakes), but it actually makes no damn sense.
The Crownlands are the size of Finland. So "good" Daeron "on their wedding day, he granted Daemon a tract of land near the Blackwater, with the right to raise a castle"... Is literally nothing. It is "your father/brother owns the entirely of Finland and gave you a nice house across the street".
Daeron could very well gave given his entire family a very nice "track of land", enough for them to raise a large family.
Even his sisters. But besides making no sense, it also shows how nobles vs smallfolk are treated in Westeros.
Falena Stokeworth is married off to a knight and master of arms who is made one of the most powerful lords of the realm.
Meg is given to her husband, beaten to death by him, possible has no justice delivered and her daughters, the youngest being not 1 and the eldest being not yet 4 are sent to be Faith by Viserys (While Naerys is denied it, and she very likely saw the being a Septa as a escape from marriage as much as sign of devotion). Because they don't matter to the royal family since their mother was a commoner.
Shiera on the other hand had many lords and knights ask to marry her. We know nothing of Melissa other children, because they are one: girls, two: not sexually involved with Targaryens, so they don't matter to George.
Again, as many like you and @aegor-bamfsteel out, this is not how medieval world worked.
Illegitimate children of Kings were more often made dukes and earls than lords (and they were made lords), they were bishops or cardinals. And the women? Henry I illegitimate daughters were duchess, countess and one was even Queen of Scotland. And even for illegimate child that were legitimized one only needs to look at the children of Katherine Swynford (whose granddaughter was also Queen of Scotland).
So, saying people like Jon, Daemon or even second sons like Bran, Garlan, and Otto had nothing and should be happy with the little they were given makes no sense in a country the size of Westeros.
I know Westeros is about the size of South America, but I had no idea the Crownlands were that large! Finland, really? And that's after the Crownlands were carved out of the Riverlands and Stormlands. It would be like "My father, who was the king of South America and had the entirety of Paraguay under his personal control, legally deeded me a few square kilometers there. Then my half-brother became the king of South America and let the legal ruling stand, as was required."
It's funny that for all GRRM's inability to stop creating barely relevant characters, he seems allergic to the idea of cadet houses. How are they too difficult to remember when half the Freys have distinct personalities? The Stuart/Stewart ruling family in Scotland briefly split into two branches, which were reunited when James I/VI's parents married. Realistically, Walder Frey would have been The Most Honorable Walder Frey, Marquess of the Twins to his ruling lord's His Grace Hoster Tully, Duke of Riverrun, and several of his children would be created The Right Honorable (First Name) Frey, Earl of (Fief Name). They wouldn't all be living in the same castle and they wouldn't be fighting over one inheritance because the name, wealth, and lands would be split. Even his youngest children might have had the title of Baronet without a land inheritance.
Sending daughters to be nuns was unfortunately not unknown when a family had dowry issues or were otherwise unable to support daughters, as well as an easy method of currying favor with the Church. Despite the famous "Get thee to a nunnery" line, however, it wasn't a punishment for being born with royal blood. It was also presented as a virtuous choice and a way to honor God. Not even the children of aristocrats and common-born partners were automatically sent to serve the Church. William the Conqueror was illegitimate and his mother wasn't noble, for example. Owen Tudor, who came from a powerful family but wasn't a peer himself (and may have been a servant), had an illegitimate child outside of his marriage to the Queen Dowager, and that child was a landed knight.
I don't think GRRM fully understands how sacred royal blood was considered to be. In England, Megette's daughters would have been a prince's children and the current king's grandnieces. Viserys would have had an ethical if not legal obligation to support their mother, whether that was giving her funds to live independently or awarding her husband some kind of high-ranking servant position in the Riverlands. She might have still been beaten to death, but he would not have sent her back out of spite. He wouldn't have even considered it.