Some guys prefer not to have to get vetted every time they want to see a different person.  Some like the convenience of dealing with just 1 contact.  Some like earning "frequent flyer" points.  Some like having a "manager" they can complain to if the service was lacking for some reason.  (Try getting some sort of recompense for a bad session from an indie.)
 
And, for some, like me, indies are not always an option.
 
Because of my life situation, I can rarely schedule in advance.  Trying to schedule with an indie on short notice has a success rate of about 5-10%.  Think of how often you hobby.  Now, imagine that 9 out of 10 times you end up not getting to see anyone at all.  Would be frustrating, don't you think?
 
You can sometimes get a backpage girl on such short notice.  For the quality, you may as well take your chances with a street walker.
 
So, that leaves agencies.
 
Yes, there is a different level of risk, but we are all on this forum because, in some cases, we choose the risk side of the risk vs. reward equation.  Seeing escorts is higher risk than abstaining.  Getting a bbbj is higher risk than a cbj.  etc.  
 
For many hobbiests, indies meet their needs perfectly, but we don't all have the same needs.  
 
I am not advocating for agencies.  They might not be for you.  But for every reason to stay away from agencies, others might have equally motivating reasons to stay away from indies.
 
To each his own

huh, not 100% true = a big well known NJ agency got busted too (no international transfers)

Besides the recent one (did international transfers), one of the oldest and most trusted madams from NJ got pinched - and she didn't have international connections.
If I owned an agency (definitely will never do but I was offered to 'open' one many times), I would operate less than a year and close shop, take a break, then reopen again.
To any agency operating as long these did, is just a matter of 'when' they will get caught.
Being greedy in our business is not the way to go.  
You get too big and operating all over the place, you get the feds attention.
That's why many guys are only seeing a handful of local discreet ladies and are completely out of the boards - not posting or writing any reviews.
People in the hobby (boys & girls) tend to forget that babbling too much about ANY illegal activities eventually will have consequences.
For the past few years, I have phased out my online persona to a minimum - I still run ads once in a while just to let people know that I am still 'alive' and around.
Due to the recent events, I am pretty much sticking to my regulars. Less money but I feel way safer

Yes your 100 % right, messing with International business will bing the cuffs and throw away the key

Some people may feel they are above the law , but walking onto USA grounds with 4k or more of foreign currency  will sting you big time, keep on doing it and you will be toast.