As a cc user and custom (for own use) cc creator I believe the reason why I don't have this issue is because of the objects I use on my lots.
There is this Tag in the Tags section called "Func_SimRay_Transform_AlienVisitor_Allow" - most every EA object has this tag added which mean to allow aliens to visit. I assume that you guys are using lots of objects with this entry included.
If you use cc and know how to use Sims4Studio you can look-up your cc for that Tag-entry.
In my case, whenever I download cc or create some on my own, I always check each download for mistakes first like wrong tags and tunings, wrong mesh shadow lods, footprint, occluder andwhatnot, before I add stuff into my game. I ALWAYS check the Objects/Tags list in the warehouse section and if an objects has this tag entry Func_SimRay_Transform_AlienVisitor_Allow, I delete it. That is is only reason I can explain to myself why I'm not having lot of Alien abductions.
I actually don't mind if my sim get abducted, I just don't like this entry in every single object which is why I delete it.
I rarely use EA's stuff which may be another reason why I'm not so much affected by that.
IMO, EA should not add that tag to most every game content.