The aliens in question aren't of a hive mind in the strictest sense (instead of many drones answering to a leadership caste each organism acts as one cell, all of them are essentially 'the same rank'). They have studied humans from afar, even covertly abducted the odd one for experimentation. Assuming one of these experiments involves genetically engineering creatures with traits of both species- what could they gain from doing so? I've considered a possible motivation being they thought the hybrids could provide insight to how an individualistic culture functions- can anyone suggest others?
the hybrids could provide insight to how an individualistic culture functions
You're exactly right:
There are aspects of an alien's life experience - different senses, different psychology - that a human cannot possibly understand and vice versa. Perhaps the hybrid was created that could experience parts of both?
If humans understand 80% of their own experience with the world but only 20% of the aliens' experience (because they are so distant from each other) - and vice versa - while a hybrid creature understands 80% of it's own experience but also 50% of each original species' experience (because it is so close to both), then wouldn't these new creatures be able to translate the experiences of the two originals in ways that the originals would never have thought to try?
What are some other distinctions you've come up with in addition to "Humans - disconnected, Aliens - connected"?
It's possible that you are aliens may want to colonize Earth or an Earth-like planet. But are biologically uncompatible with such a planet. It wouldn't make sense for them to create hybrids that were biologically similar enough two humans to colonize the plant, but still retain their hive mind sense.
The main reason I can think of is that the aliens realise that they have certain drawbacks that prevent them from accomplishing their purpose/mission on Earth. With selective genetics, they could create an alien-human hybrid that possesses the strengths of the alien and also of the human. That way, if they want to colonize/take over the world, they have the perfect species to do so: a hybrid that maybe looks and behaves like a human and can survive in Earth's atmosphere, and yet is subject to the group mindset and follows the bidding of the pure aliens.
The above scenario could be if aliens are new to the world and thus have (perhaps) sinister motives. Alternatively, in a Star Wars environment, where aliens are already an accepted part of life, such a hybrid could solve the problem of boundaries and citizenship. For example, in current climes, if a German father married an Asian mother, their children could possibly be citizens of either country. Thus, the same concept could be applied with respect to aliens, where the aliens would then strengthen their footing on Earth.
Maybe this is how the aliens evolve themselves. They discover new organisms, the hybridised some individuals, and they keep them in their "society" for a trial period of time. They can observe then if this additions bring any benefits to the collective or they just eliminate the individuals and move along to another species.
Maybe make so humans are not the only species on earth they have hybrids of.
There are plenty of scenarios...
Perhaps they are seeking escape from a weakness in their own biology. It could be a particular vulnerability to illness, or a specific plague that has destroyed their home world. Their mission is to create a hybrid species that can re-colonize their home world.
Or, simple selective breeding. Their mission could be to create a super-race, and they selectively collect and breed traits they like into their society. Perhaps different classes of citizens, warriors, leaders, etc, each target different traits.
Or, their race has become sterile due to a plague. They cannot reproduce, so to survive, they are seeking other organisms that they can hybridize and preserve as much of their genome and culture as possible.