I am not sure why this happen.. (process problem)

Why do you disagree? We basically say the same thing. Signals that "feed" the process and signals that are "read" in the process mean the same thing for me. And in this case the only signal "read" or "feeding" the process is bin_result.

But I don't agree on the latches production though ;) As I said Quartus will ignore the sensitivity list and just create a pure combinational process, whatever the sensitivity list is (just try it and check RTL viewer). Latches are produced if you have one or several outputs that is only set in some paths in the process. In the code here bcd_result is always affected a value so no latch will be created.