This may be true but it's also one of their goals not to really add new features. st and dwm both have some "3rd party" patches for some features that some people might want.
I'm not sure whether that's the right thing to do but it's the way they work.
I've used St and have written some patches myself to add minor features I wanted. I get the impression that they intend it to be a small core for people to add features themselves if they want. They implemented the core features that people can all agree on, then leave it as an exercise to the reader to add other stuff. Dwb follows a similar approach, I think.
That said, I moved on to ROXterm because I was having encoding issues with a couple of programs I use. St is worth consideration as an uber-minimalist terminal though... it's very fast. Even on ancient hardware it launches essentially instantly because it's not loading any large libraries like GTK. St is pretty fun to hack on, too.
I'm not sure whether that's the right thing to do but it's the way they work.