I've been reading through the new Monster Manual and two things in particular have stuck out.

First, there are creatures like the aboleth and arch-hag that can inflict curses on creatures. However, the trait text says nothing on how the curse can be lifted/cured. Is the unstated assumption that the remove curse spell is the expected/canon cure?

Second, I'm seeing very few cases of the use of the bloodied trait. Am I missing it, or is it just a relative handful of creatures?

Unless noted otherwise, curses can be removed by the Remove Curse and Greater Restoration spells or other magic that explicitly ends curses.

The ratio of monsters traits or actions relying on being Bloodied remains few and far between as its used with parsimony in general.

Weird to reintroduce a rule like that only to use it so sparingly.

Bloodied was something from 4E that got carried forward in the community as being a useful term for "Below half health."  I guess WoTC is reviving it for a few things to see how it does. If people don't like it, it doesn't matter as much because it is rareish.
it feels like we are playtesting the new edition/revision still.

Remove Curse and Greater Restoration are the stated means of removing curses of all type - however, the DM is free to add additional conditions onto its removal (such as special rituals, rare components, etc.). For example: When I inflicted lycanthrope upon a character in one game I ran, I ruled that the Remove Curse had to be cast during a full moon, and simply allowed the character to retry the save to resist it (it took 2 attempts before it was cured).

According to the Player's Handbook, Remove Curse and Greater Restoration are all that's needed. I believe it states somewhere in the DMG that DMs are free to add to that, and of course, DMs are always free to modify anything they wish.

I liked a previous edition's method of lycanthrope removal, so I combined that with what's stated in 5e to what I listed above. But that's because I don't like how pointless many curses, poisons, diseases, inflictions have become (diseases are now rolled in with the poisoned condition) - all can be removed with fairly common spells to the point that no one fears them anymore (nor has to play a character inflicted with one) because of how easily removed they are. As such, I add additional hurdles that must be accomplished before or during the casting in order for them to work.

Quote from Xukuri >>

First, there are creatures like the aboleth and arch-hag that can inflict curses on creatures. However, the trait text says nothing on how the curse can be lifted/cured. Is the unstated assumption that the remove curse spell is the expected/canon cure?

Curses are in the rules glossary, when they call it a curse you can assume it follows the rules for a curse.

Bloodied is just a convenient way of denoting "below half HP", which some things in the rules already referenced.

Thanks, all. I keep forgetting to check the rules glossary for entries. Might be the best innovation of the new books.

The term Bloodied was referenced in Dungeon Master Guide 2014

Players often ask how hurt a monster looks. Don’t ever feel as though you need to reveal exact hit points, but if a monster is below half its hit point maximum, it’s fair to say that it has visible wounds and appears beaten down. You can describe a monster taken to half its hit points as bloodied, giving the players a sense of progress in a fight against a tough opponent, and helping them judge when to use their most powerful spells and abilities.

I usually give them an estimate related to % of total hp. 75%, 50%, 25%, and barely able to remain on their feet. I think those are reasonable thresholds that someone should be able to figure out when seeing a creature or person fight and take hits.

I also play under a DM that basically just says the monsters are "scratched" or "hurt" and after several multi-year campaigns, we still haven't figured out exactly what those terms mean - and as such have simply stopped asking.