Basically, it is all in the cost
For beginners who start off with FOWLRs, they usually have a small budget
With that, they'll get poorer quality rocks and usually skimp a little at almost everything.
For a successful reef, that reefer might need to purchase better rocks, redo the aquascape, purchase better equipments and such
And not to mention about removing fish that are not reefsafe
So that might as well sums up a tear down right?