I have the feeling that quite a few players see the 'free' battles as more than what they really are. Like something where you could walk away regularly with $100's or even more in withdrawals.
The Battle of Slots, especially the Free Battles, are primarily a social gamification tool that enhances player retention as well as average time a player spends in the casino. And you can rest assured that the VS team did their risk calculations properly as to how often it is likely that somebody will run the few bucks won from Battle FS up into a big withdrawal, that is just common sense.
Hint: deposit and wagering needed to qualify for the Free Battles. E.g. 4,000 players wagering min. $500/week = $2Mio, that leaves some room to have a few rather unlikely larger withdrawals covered. And remember, players have to re-deposit to qualify for the next week of Free Battles.
Now think, how often do you deposit $20 and make it to a sizeable balance? You'd be happy to get 30mins - 1hr playtime if things go normal. The Free Spins from the Free Battles rarely pay more than $10 even when you have 25 - 100FS. I won a Gemix battle last week and got just over $6 from the 100 spins, I remember once winning the 750 Free Spins Battle on The Invisible Man, first prize was 75 FS then, which paid $3.57
I see the Free Battles as pure pass time which let's me spin some reels for a few minutes every two hours. And since I work from home on the laptop every day, it is a nice break in between. Nothing more! Ever since they were launched I made it once from $12 FS winnings to a $650 withdrawal (5 scatters @ $0.27 on DOA) and that from an average of 5 battles per day, take that times some 500 days since they launched and it amounts to 2,500 battles that i played.
In closing, i think is totally wrong to get your hopes up that the Free Battles and winning some FS will be the 'saving grace" that lead to regular big withdrawals. But you can always have some fun without having to deposit.