The short answer is "absolutely." At minimum, a boon is something you can give up as damage when some monster cracks your skull open. But there's another reason: your fellow adventurer might want you to give it to them.
This is sometimes trickier than it looks. To give a card to someone, you must start your turn at that character's location. They might have to come to you to get it, assuming you even still have it in your hand when they get there. Coordinating a timely rendezvous can lead to a villain's untimely demise. Even if the boon isn't critical to the moment at hand, it can be worthwhile to acquire it for your friends-remember that you can trade cards in between scenarios.
Things are much easier, of course, if the character who wants a particular boon can get it on their own. If you're able to look ahead in the location or evade cards, you can tell another player about a useful card. Then they can spend their turns trying to get it and you can get on with your own goals.