The program only idles games which have cards available. If all drops have been allocated to you already (which is 50% of 1 single badge level because that is how Valve made it) then idlemaster skips the game to focus on what games still have cards waiting.

Some games also do not have any cards at all. These games are skipped as if they had 0 remaining.

Idle master reads your badge page looking for the words "card drops remaining", see your badge page.

Ah okay thank you, i was assuming every game had cards that dropped.