Actually this procedure is not so obvious at all. It makes an assumption – that the leper wants to be cleansed. It then says that in order to cleanse him there is a set procedure. How about a person who does not, for whatever strange reason, want to be purified?
Don’t ask why a leper should be so stupid as to want to keep their status quo. People have their own psychology. Illness of any kind is no blessing in the opinion of most of us, but there are individuals who are exceptions to the rule.
The assumption the Torah makes is that any normal person wants to be better. It makes a second assumption, that healing is not only desirable but possible. From the Torah point of view, any illness, physical or mental, must have a cure somewhere, and it is the task of the medical profession to find it.
Judaism never said, as do certain other religions, that illness was part of God’s design and human beings had no right to intervene. We honour the physician because they are doing God’s work.