To kill fools using primitive firecracker-powered slugflingers. [Energy Weapons 75]
Er... Science! Rigth? If they can do it why not make hundreds of them right?
Yep.
Why androids?
http://tvtropes.org/pmwiki/pmwiki.php/Main/ForScience
Seriously? It's a radiation, FEV-infested world in which armed threats are ever-present. Androids suit the high-risk environment like nothing else, and the only better thing than a general purpose robot is a robot that passes for a human.
They don't feel pity, remorse or fear, and they will absolutely not stop, ever, until their enemies are dead!
The problem is that they gave the human robots enough intelligence to not like being treated like appliances and disposable catspaws. And then they made up a system to "retrieve" runaways while refusing to ask "why are they running away".
I can think of a few reasons...
1) Bed partners...especially if a significant number of Institute faculty were ghoulified during the War. Why force yourself on your slaves when you can build your dream girl/guy and program them to want you passionately?
2) as the prototypes of a program to create hosts for their brains or downloaded themselves into it so they can live forever (without being ghouls) ala the BSG reboot Cylons. The AI level intelligence androids have suggests the latter....an artificial "brain" intended to hold the uploaded person would have to be extremely sophisticated. But it creates a problem as the androids keep "waking up".
3) An attempt to create a army of compliant slave soldiers/workers that has been somewhat botched as they made them too smart and they became true AIs, which if Zimmer's opinion is common in the Institute they don't realize, who want to live their own lives.
4) Because in addition to one or all of the above, doing so successfully would be one of the greatest feats of engineering in the history of mankind. Or in other words....FOR SCIENCE!
5) Not to mention, achieving 4 would win the scientists responsible the adulation and jealousy of their peers...the only people whose opinion matters to them.
I assume they provide in their more basic form reliable workers and trust worthy security guards.
In the top of line 'human' androids you have great potential but obviously some problems though making them to human, of course long term we know that its possible in the Fallout universe to use human brains with robots, so if you can create a lifelike durable 'human' body and join that up with human brains, you have the possibilty of members of the Institute living very long productive lives.