Mildew and odor form on front loaders for a couple for reasons. Water
pools at the bottom, but on the other surface area of the outer tub,
water just sprays onto the surface. If you add soap scum in the area
of the outer tub that gets very little washing action of water, this
makes a potent breeding ground for mildew and odor, As far as the
rubber boot goes, this forms mildew due the properties of the rubber
itself, as well as the presence of water and humidity.

Why replace the outer tub in order to replace the bearings? The
bearings on a front loader carry a lot of weight. The bearing has to
be set into the tub strongly. This doesn't leave much room for ease
of removal.

Let me add one additional thought about...Consumer Reports. I have
read their reviews on laundry machines, and it is as if they don't
really know what they are talking about. For example, they rated the
Calypso washer, one of the worst designs of all time, very highly
until the bitter end. Instead of rating model numbers, which change
at the designer's whim, they really should rate platforms, the
building foundation of all machines. Here are the only platforms that
exist on domestic machines, both in traditional and non-standard
agitator (NSA) designs:

Whirlpool top loader and Cabrio NSA
Whirlpool Duet full size front loader and the smaller Sport (which is
slightly different from Duet)
GE top loader, and GE NSA (I forget the name of this).
Frigidaire top loader and front loader

This pretty much covers the entire field of washers. All other brands
are just brand-engineered on these platforms. For example, the GE
front loader sold at Home Depot is made by Frigidaire. All Kenmore
machines are covered in the list above. All Maytag machines are
rebadged Whirlpool machines, Amana and other Maytag brands too.

Odds and ends...There is a larger GE front loader rebadged from Asia,
Korea I think. Don't know if this is currently on the market. There
was an interim Maytag front load washer from Korea as well, marketed
after the Maytag Neptune, until Whirlpool bought Maytag, then it was
deleted.