T-Hob, word "versatility" stated by Bones stands for not only speed changes. It also includes changes in axis rotation, axis tilt and rev rate.
As long as you are "versatile" enough to adapt to the conditions, you won't need to alter the surface much.
However, there are times that versatility simply won't be enough. A solid bowler should/must practice different releases and speeds. Consistency is a must here. But, in the end, I believe that every bowler has one "basic" delivery, unique to him/herself. That is his/her nature. Even if one practices different releases, those releases will be based on his/her nature. In other words, my maximum and minimum releases can be different from yours.
Furthermore, even with long and hard time practice, I believe one can alter his/her release no more than 3 or 4 (Consistent variations that can be repeated over and over again).. I may be wrong of course, but that's my opinion..
Yet, every ball has its limitations to handle a specific condition even if you apply different release/speed combinations. That is why all serious bowlers come up with an arsenal. When a ball do not give desired reaction on a specific condition (even with your alternate releases/speeds), and no other ball in your arsenal is close enough to your needs, surface preparation becomes a must.
Also there can be other reasons. Sometimes you need to adjust surface to change the original reaction, if I may say so.. You might need to scuff to eliminate the over under, or polish to get some more length and backend. I respectfully disagree that it is "massing up with the ball's surface..
I believe that there are too many variables to get the optimum reaction and adjusting surface is one of those together with versatility of a bowler. I also believe that altering surface and changing balls is a part of bowlers' versatility, as well as his/her ability to do different releases and speeds..
Regards,
Burak