The opening sequence of Tangled explains its follicularly gifted heroine's origin in a magic flower with healing properties discovered by a woman named (somewhat erroneously at this point) Mother Gothel, who uses it to stay young and beautiful. When the kingdom's pregnant Queen falls ill, the royal guard searches for the magic flower. They bring it back, and she eats it, healing her just in time for the birth of a now-magic baby that is immediately kidnapped by Mother Gothel so she can keep using the flower's magic. Rude, right?
But is it? Look at this from Mother Gothel's perspective: They stole her shit. Insofar as natural resources can be owned by a person, which is a whole thing, it was clearly discovered by Mother Gothel. She was just reclaiming her stolen property, and she was probably as dismayed as anyone that it had since become sentient.
At least Mother Gothel left the flower in the ground. There was no reason the Queen couldn't have been carried by an army of burly men to the flower or eaten a soup made from a single petal, but like the imperialist dicks they are, those burly men just tore the flower out of the ground without even considering not destroying a magical omnipotent plant doctor. Sure, Mother Gothel wasn't exactly advertising the flower, but if the royal guard knew about it, it was known, and theoretically, anyone could have used it. She probably hid it precisely because some entitled asshole was bound to steal it sooner or later. It's not like its power depletes with use.
Now that power is held exclusively by the heir to the throne, who is definitely a decent person who would probably be happy to heal all her subjects. But does she? We only see her use it on her boyfriend. She meets tons of injured and chronically ill countrymen on her journey of self-discovery. Does she try to heal any of them?
It's understandable that she wouldn't want to spend 18 hours a day healing everyone who comes to her door. That's a big responsibility to lay on one person ... and it wouldn't be necessary if the royal administration had just told everyone, "Hey! Healing flower over here! Everybody, come get your heal on!" Oh, well. Monarchies gonna monarch.
Top image: The Walt Disney Company