There are a variety of answers to this, depending on the feature.
I’m not sure what you mean by ‘to one’ display options are limited to ‘compact lists’. Are you talking about entity view? If so, then it’s just how the entity view improvements have been prioritised. If you want to be able to see other fields belonging to the linked entity, then perhaps this is something you want to vote for. Or may be there are other feature request topics that are closer to what you need.
Again, it’s just a case of prioritisation.
This is also a question of priorities, but bear in mind that we already have comments/complaints about the complexity of the context filter UI, so adding more relations would make this even worse 
We plan to improve context filters at some point, and when we do so, it may open up the option to add in routes which traverse a to-one relation.