A lack of professionalism, maybe, but more a lack of "skilled guys" with balls to test them. How many LHW's and MW's might fare well in the HW division if they didn't cut weight to duck the big guys? Fedor was a perfect example of the skilled smaller guy taking on the big guys. Throughout his career, he has been smaller than jon jones, Costa, Anthony Johnson (RHS), Rampage Jackson, Chuck Lidell, Tito Ortiz, Anthony Peirera and the list goes on.
Overall, if the big right hand wins you fights against most guys you face, why fix it if it ain't broke.