[moe]

I was optimizing for the total network throughput of the bathroom.

But you didn't. You have serialized access to two resources that were previously independent.

Since a significant portion of users need only one of the two resources you have created a new point of contention. For access to the faucet not only do I have to wait for people washing their hands, now I also have to wait for people drying their hands.

[petsos]

Yes but one of the resources (the dryer) has increased significantly too. And since we are both using the word "significant" instead of any real numbers we can prove either point.