gambling isnt work, unless youre a professional poker player, but even then the income might not be steady as that would depend on your luck and opportunities to win.
The "steadyness" of the incoming in this case would be directly linked with your skill level, and the type of poker you are playing.
For example, the incoming of a someone who multitables 9man cash games or 1 tables sit'n'goes will be pretty damn steady, but it will be a massive grind. Hours or work that will take a ton of stamina.
Its a different story for players that focus on playing large tourneys with huge prizepools, they can have streaks of breakeven and losing months very easy.
which is why it qualifies as work for the few that are skilled enough where they can treat poker as a job and make a decent living off of it. maintaining that level of play to consistently turn a profit takes incredible mental endurance, its far from "fun" for these people. for the majority of addicts here that claim to gamble for fun though, its more than a bit likely they will never maintain a steady stream of winnings and even come close to thinking of poker as a job.