Every time I see people asking if this is a new phenomenon (or strongly implying it is) I have to laugh.
Here's the scoop -- I've seen people who had frontloaders in the 60's and 70's and some of them were super gross with mold/mildew and some were so clean you might as well think they were brand new.
When I was living in South America in the 80's, Whirlpool started distributing a couple of models of a British version of the Philips frontloaders under the Frigidaire brand, and my family got one. Then friends and neighbors got the machines when they saw ours and how well it worked. Over half of the machines stayed clean as new too, and some of them had varying amounts of mold/mildew -- all of the ones that were contaminated seemed to only do cold washes and/or stay closed most of the time, while the clean ones spend most of the time with the door at least ajar if not open, and the dispenser drawer removed or ajar.
At this point, one could think that maybe water quality has something to do with it, and maybe it does for the majority of cases. But one case in particular is very interesting to me: when I moved out of the home, I left the washer for my brother and his family to use, and it got a small amount of mold/mildew -- they were using the same detergents and water I was using, but lower temps with mostly cold washes, and they were keeping the dispenser drawer and door closed because they had kids. Of course, when I visited, I would quickly clean the machine for them and it would stay clean for a while, but the cycle repeated.
So, maybe there are people out there that do everything right (high temp washes, good detergent, air out dispensers and tub) and still get problems, and maybe sometimes it may be that some machines are made with substandard boot materials etc -- but my money is mostly that people aren't using the machines the way they were supposed to.
And this is not reserved *just* for the "dreadful" frontloaders either -- all my life I've seen people who owned toploaders of all kinds ("water hogs" from the 60's to brand new HE toploaders) with the same problems. My gut feeling is that it's always the same old thing, people who aren't airing the tub after wash day is over and people who overload and/or use all cold washes and/or cheap detergents have the problem.
In my experience, it's very rare to see people who have blinding white and bright colored clothing have problems with their washers having mold/mildew -- it's somehow only a problem for people who have muted colors and dingy whites, and people who complain about spots being left on their laundry. In the few cases I've asked for details because they were complaining and asking me for advice, they were using short cycle times, lower temps and either overdosing or underdosing detergent, and most had no idea if the machine was rinsing well because they never hung out near the machine not even every once in a while to see if everything was going according to plan -- they loaded things up and disappeared for several hours, firmly believing that if the laundry was cycled thru, somehow the machine would have done everything properly as it it were Rosie from the Jetsons.
And I'll grant them that *some* modern machines can repeat rinses until clothes are well rinsed but most machines don't do that or just get rid of the oversudsing condition, but do not rinse enough.
And as usual, YMMV.
Cheers,
-- Paulo.