Sim not using counters in kitchen to prep food

Truly a mystery when it happens, I agree

I've seen this too. 

And also, if, let's say, I have an indoor kitchen and then a partial outdoor kitchen, even though they're initially inside, they'll go all the way outside to chop on the outside countertop and then return inside to finish cooking. It needlessly wastes time for them to keep going back and forth just to cook on their favorite countertop instead of the nearest.

I removed counters from a bathroom in a maxis built house because this was driving me nuts. In another house I just added clutter to the counters outside of the kitchen. 
I have no idea why they have started walking past available counters to prep food but it's not just prepping food that's the issue, they often ignore the closest table to eat at now and the closest bathroom to do their business! Seems like the shortest route command is no longer there in some cases!!!

Yeah I have a kitchen table in one of my builds and sims will trek all across the house to another table or even go somewhere outside instead of using the perfectly fine one a few steps away. It's really annoying because you have to wait for them to go there else they will just leave the plate on the floor somewhere. 
Often I'm just sitting and marveling on the trip around the world they're doing... 
Also when they've finished preparing a meal they'll also put it way over somewhere vs just putting it on the counter next to them. 
I have a big build ( Residential business) where I have a perfectly fine kitchen but they ( when hungry) go all the way into the business and start cooking on a counter in there instead of where they are. It's pretty far so really makes that lot unplayable unless I lock/unlock doors all the time.