Another curiosity question

While riding on Cape Cod this weekend, my co-star came up with an
interesting (to me) question: Why do the front and rear shifters work
opposite to each other? Further explanation. We both have Ultegra
integrated shifters. On the right (front), clicking the larger shifter
moves the chain to a larger ring closer to the frame. On the left
(rear), clicking the larger lever moves the chain to a larger ring that
is further from the frame.

Why don't both larger levers move the chain the same direction?

Thanks,

Tom Weaver