Just Troll Comments, no real PRO still uses CD/DVD in any workflow, Pendrives does de job 10x faster and much more reliable w/o waste.
And Why somebody is worried about CD/DVD on a 5000$ Mac? Who Spend 5000$ to burn CD/DVDs all the day, thats idiotic, troll questions.
If there still people requiring to burn a lot of CD/DVD, a Mac Mini with an external HEAVY DUTY EASY TO REPLACE CD/DVD/BD BURNER WILL DO for about 800$ or about 1/6 the value of an Mac PRO.
When it comes to computers I am completely serious about the optical drive, I imagine others are as well depending on their ends. I do not personal burn data to dvd's, never did with flash drives. Some do because of cost and they have make it clean they want it internal.
And that could be one of the points, if you spend $5,000 on a computer it should have everything you want.