If we ever did add checkpoints, it would be apart of some sort of optional easy mode for sure- and a lot of tweaking would be evolved with that mode. Not just checkpoints, because like you said, it would be far too easy if it was just that.
Viewing post in Sun Runner: The Four Ancient Masks of Sun Land jam comments
Oh yeah for sure, if this was a full game then you'd want people to replay it to gain that mastery, but for a jam game it's going to be hard to convince people to spend that long, especially when they have a hundred or more other games.
Usually it's a good idea to let players experience the whole game in about 5 minutes, with maybe more to do if they end up really loving it.
But also there is no mandate to make a game that works especially well in a jam setting! it's just as valid to make something more like a full game, the only drawback being that most the people rating it won't see all of it.