Memory backup capacitors: why a capacitor?
They're cheaper and (rightly or not) in product design that's often an argument which overshadows a lot of technical arguments.
And, like you said, capacitors don't require special charging electronics. Also, batteries contain chemicals for which you have to comply to special regulations. (Sometimes this is the reason why toys and such are delivered without batteries.)  

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Another thing: batteries are not suited for wave-soldering. You'll either have to solder them manually afterward (cost), or, like for coin cells, use a battery holder (cost) and add the battery manually (cost).