Well I did mention that it would be good for a new person just starting out, that way they'd have a good basic understanding going into this industry
But being IICRC certified doesn't automatically make anyone a good cleaner no more then having a drivers license makes anyone a good driver, being a good cleaner comes from experience over time and reading on some of the forums is also beneficial
It as well can be used as a sales point in possibly getting new customers but I think if one were to tell a customer they've been in the business cleaning carpets for 15yrs 20yrs or more that would be something a customer can relate to, saying that your IICRC certified puts a blank look on their face as most don't know what it is and have never heard of it.
Bottom line, I would recommend it to someone just starting out for sure, also would recommend reading the forums as well.
And they can do what I did in the beginning and sometimes still do which is to go to a local store that sells and installs carpeting as they will most always have a lot trashed carpet that they pulled from someones home in their dumpster, ask if you can take some (i've never been told no) take it home and practice and experiment on it.
Sometimes i'll still do this when trying a new chem out and to compare it to others i have and use