Why should I bother packing my drugs if it doesn't get them out any faster?

One available machine in Big Pharma is the Drug Packer, which (at its un-upgraded level) allows you to combine two identical products into a box, which can then be sold as a single unit for twice the revenue. (Profits will suffer due to the added processing cost.)

However, this machine only has one input, and can only add one product to a box per day, meaning that its output is necessarily slowed to one box (of 2 products) every two days (or 1 product per day.)

Without the Packer, your stream of products can be shipped directly to the output port at a rate of 1/day - the same as when using the Packer.

It therefore seems that packing your products has no apparent benefit over simply shipping them in single units - in fact it may be worse because you're paying to pack them.

Is there an optimal method for using the Packer in a production line (specifically a method that will reduce my operating margin and/or accelerate my revenue growth)? Is there, perhaps, another machine that should be used in conjunction with the packer to achieve optimum efficiency?

It is for using the available input/output slots better. With packers you need 2 inputs for one output, while without you need 2 inputs and 2 outputs

I like to think of it as upgrading from a 2:1 ratio of sockets per line (spl) to a 3:2 ratio. If you've got 6 sockets that's 3 lines (2:1) or 4 lines (3:2) with 4 packers.

I like to think of it that way because in a room with 7 sockets I can get 4 lines - 2 lines at 2:1 spl and 2 at 3:2 spl. I cannot get 5 lines, and while I could get 4 at 3:2 spl and have an empty socket left over, I'd have an unused socket and use 2 extra packers to do it.