Since some of you have been asking, the Lotto collection gives "+10% to job loot drops" as its reward. I would assume this is an additive bonus rather than multiplicative.
In other words, if an item had a 30% drop rate, it now has a 40% drop rate. This might sound great at first, but the odds of winning a piece are very slim, let alone collecting the whole set. You would have to trade for the set & contend with scammers. The problem pieces for the set go for anywhere from 50 to 100+ TNT/guerrilla squads/other high-end items.
So good luck collecting a set! Unless they make it more accessible, it just does not seem to be worth it to me.