Given the average price for an NYC apartment at north of $3k, the cost to a landlord of complying with the law even once looks significantly higher than the cost of the paying the fine.
Remember, broker's fees don't go to the landlord. They go to the brokers! The only reason landlords use them is because they're free for the landlord.
It's absolutely cheaper for the landlord to hire a service than to pay a fine.
I'm pretty sure there are landlords that charge the brokers for the chance to show their units. The landlords can advertise rents that are $300 lower (but get a $500 cut of the broker fee), and then can raise the rent by $300 the next year, increasing the chance that the tenant will go to another one of their (or their buddy's) properties and pay another brokers fee.
And the last thing a landlord generally wants is for their tenant of just one year to leave. Remember, an apartment will often go vacant for a month or even two between tenants, which is lost rent.
And if your tenant leaves, chances are miniscule they happen to move to another property you happen to own. (And what does a "buddy's" property have to do with anything?)
(That's assuming apartments even stay empty that long; when we were searching, we almost always had to commit to an apartment the day of the showing, or it'd be off the market the next day. Apartments seem to stay empty long enough for the required cleaning and maintenance to take place - and sometimes barely even that long, we've viewed apartments that were being actively worked on.)