I was wondering lately why the air induction on many aviation engines bring the air/fuel through the hot oil sump after the carburetor. Seems like it would rob a few horsepower. What's the benefit or engineering purpose? Fuel atomization?

There are several actions involved.

1- It does help atomize the air /fuel mixture

2- It prevents any ice from forming downstream of the carb.

3- The additional heat hurts the HP out of the motor because the VE = Volumemetric efficiency is reduced.

4- It helps cool the oil to a small degree.

5- That config is easiest for most installs to work with and it is the closest path from the carb to the intake valve.

Im no engineer, but I'm gonna guess its because of limited space in a typical airplane installation.

If they moved it aft of the sump, the engine would need to be moved further forward, or the firewall further aft. If they modified the shape of the oil sump, it would most likely be smaller with less capacity.

Just a guess

Ben has made some good points.

It may also be simple ergonomics. The obvious place for a carb is underneath (or atop) the engine, if you want to minimise the length of the intake manifold to a boxer engine (minimise weight). If you want to maintain good prop clearance, the crankshaft needs to be as high as possible, so there isn't much room atop the engine for a bulky carb & air-scoop. So underneath is a good choice.

In the same breath, a fair few fuel injected TCM engines have the throttle body on top, as this configuration can be far more compact.

Maybe the engineer was one of those kids that blow through a straw just to make bubbles in the milk or he was related to Lawrence Welk.

My engine is set up this way and it hardly ever needs carb heat because of it. It is sort of a pain in the butt because you have a potential leak at both ends of each induction tube as well as with the octopus built inside the oil pan and where the carb attaches. A single manifold or plenum would be a lot simpler. When these things were designed trucks, tractors and what not sometimes had intake runners that ran a long ways from the carb to the engine.