For lower level pros, such that I consider myself, having accounts at one of the larger "national type" banks, such as BofA, reduces the need to carry so much cash through airports or in cars, when traveling in the states, since there is a branch in many destinations. My BR is only in the $40k range and I don't need access to it all at once, so I can just go to the BofA branch in vegas, AC, reno, ect and withdrawl 8K, which keeps me under the CTR limit. When depositing, just break up the deposit into a couple days if necessary.
Pros with 100k + BR can use the banks as well, instead of carrying around large sums of cash. Of course they are going to generate some CTR's at those limits, but if you are playing at that level you probably already have to claim/explain your blackjack play/income to the government at least in part, so explaining some CTR's isn't difficult.
Just doesn't make sense to have tens or 100's or thousands of dollars on your person or vehicle any more than absolutely necessary these days. Some two-bit thug who is robbing you in hopes of getting $20 for his next fix, could walk away with half your BR!