Ive been driving and maintaining my own vehicles for over 30 years,
My wife has a Kia and in order to maintain the factory warranty she is required to take the Kia into a Kia authorized service center and when she took the Kia in for it’s10yr routine scheduled Maintenance they flushed all the fluids in the Kia not just the normal fluids like transmission oil, motor oil, Engine coolant, they did the Breaks, and Power Steering fluid flushed and fill…
So even though it never occurred to me and I haven’t done these other fluids flushing on a regular basis, I dont see any harm in doing them on my vehicles that I maintain myself from now on especially since the upside is it would flush out any contaminants that might be in the fluid and the fluid itself isnt very expensive so if in the long run it prevents from having a possibly more serious and expensive repair years from now(R&R a Master cylinder or Power Steering Pump).
Oh while you’re doing a power steering flush if there isn’t a power steering fluid filter you might want to take this opportunity of installing an in line filter at this time its an inexpensive addon!
But I’m going to suggest that OP not let them do any of the work, and take it to a local, independent mechanic with good reviews to do the brakes and transmission. My reasoning is that if they’re willing to sell wallet flushes then they’re untrustworthy. For all we know they won’t even perform the necessary ones. I don’t give money to untrustworthy businesses if I can help it.
You are not required to take any make of car to the dealer for maintenance fork to maintain the warranty, It is a matter of law. You are required to have all the maintenance work done specified in the maintenance section of the owners manual, not that recommended by the dealer and most manuals don’t call for flushing anything.
Also, why did you revive an 8year old thread?
Seeing he joined at the same time he posted, I wonder if he joined just to revive the 8 year old thread.
Seems to be happening a lot lately.
I’m going to suggest that the OP probably resolved this 8 years ago. 
Yeah, I completely missed the dates this time around. Oops.
It would be nice if there qas a red flag on any post revived after a year. Usually my first clue that I am reading an old post is when I see a reply from transman.