The new ABS systems have a lot more moving parts that are not rust resistant, some of them with smaller holes to control brake fluid.
That being said, unless your car never experiences dew point temperature changes, Dot 3 & 4 brake fluid absorbs moisture when cooling down, more so if the car is parked outside. Water equals rust, very bad for the ABS unit itself which is first in line to receive that moisture and start rusting.
Pre ABS, flushing was recommended at 60 - 80K for your brake system, because that's how long it took for moisture to start affecting braking and internal rust damage to the wheel cylinders/pistons. Go back in time and you'll find all kinds of internal rusting issues at about 40K when rear ABS was first introduced to the pickups.
In other words, unless you've installed Dot 5 (silicon based) brake fluid which doesn't absorb moisture, it is very prudent to have your brake fluid flushed every 20K to 25K miles.
If you're a DYI'er, this little tool makes flushing brakes a one man job that takes about an hour start to finish.
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Have a good day.