Why do my replies go to the person who sent the message and not to the list?
This is by design. See the article “Reply-To” Munging Considered Harmful for some background.
Also see this explanation from Danny Yoo:
Let us take a hypothetical situation. Let’s say that there are two people, say person J and person D. And say that D wrote a slightly unfriendly reply on Tutor that didn’t sit well, and person J rightfully responded back and wondered why D was so curt.
It might be embarassing if the mailing list default was to have J’s reply go directly to the Tutor list rather than to just D. Again, it might not, but who knows? If Reply-to munging was turned on by default, it would make such a mistake very likely.
(And in the end, D might want to apologize to J; D was having a very busy day today. And it might be embarassing to have that automatically posted on Tutor too. Who knows?)
We want to allow people to have the opportunity to easily respond in private, particularly for cases like this.
All of this is purely hypothetical, of course.