Don't use glue and use screws makes things easier to repair and won't affect Apples overall production. Does it really matter if a robot is gluing or screwing...
Actually, yes. Screws are harder to apply correctly than glue, regardless of whether it's a human or a robot doing the task. One glue strip is cheaper than a dozen or more screws. Machining screw holes and tensioning screws requires more quality-control. A robot capable of affixing multiple screws at one time is a more complex device to build and maintain, a robot that sequentially fastens a series of screws more complex to program, with slower throughput. Further, screws can come loose in transit, while glue is far more vibration-resistant. Hence, fewer defects, lower initial warranty claims. Back when I was taking broadcast and recording gear out on the road, I appreciated the equipment that had Loc-Tite applied to each screw (until it came time to open it up). As a carpenter would say, both screwed and glued.