This was the explanation given by Maxis back when we had a "Tech Talk" thread:
https://forums.thesims.com/en_US/discussion/comment/12637110/#Comment_12637110
"SimGuruMax;c-12637110" wrote:
"BarbaricSpaceWhale;12636496" wrote:
@SimGuruMax Do Sims prioritize sinks in the same room they cooked the food in? That seems to be a good solution since there are sinks in nearly all kitchens. If not, as long as it's feasible it seems like it's worth doing.
It's not that simple, but the short answer is that they will prefer closer objects to those that are farther away. Keep in mind that this system needs to work for all cases as we tried to make it as general and extensible as possible. The same system tells your Sims where to clean dishes as the one that tells them where to sit to eat, so the tech has a lot of masters and a lot of use-cases. We try not to special-case anything and let our design team get creative with the special-sauce like this (it is possible to add special scoring in some cases).
We will probably address this eventually but we also have a lot of other things to integrate into our system right now and we have to prioritize.
There's more discussion buried in there, if you want to weed through it. But, it sounds like the mod @taydev mentioned might be decent fix already.