Sometimes Casinos offer new affiliates a "special promo" in the form of a NDP or exclusive promo to kickstart the campaign. These are usually only valid for a specified period (1 month or so).
Now after the bonus expires, some affiliates may not take down the promo codes, even though the casino does not offer the promotion any longer. Sometimes they know that the player won't get the bonus, but figure that if he's gone to the trouble to sign up (for the NDP), the player may actually make a deposit.
Then of course, you get other sites that would see the promo code, and without knowing what the terms or timeframe of the bonus offer are, would copy it to their own sites.
The procedure her is to contact the affiliate concerned, and send them all the info they might require to change to offer to a valid one, and then when push comes to shove, eventually threaten to close the affiliate account if they do not comply.
I can see how this may look like the casinos are luring you in with a No deposit offer, and then trying to sell you a deposit bonus, but ultimately, the CS person is just doing their job. They'll have a list (or whatever system they use) of active promos, and when a client comes in to claim one, check it, see the promo is not there, and then offer an alternative from what's available to them.
It's akin to me telling people that Kmart are selling computer chairs for $4. People would flock there, and the poor sales person there would obviously not honor my offer, but at least try and direct people to the most relevant offer that IS available. Some people may actually buy something, seeing as their there already, but those that don't can't really blame Kmart.
The net is a big place, and even though the programs try to keep an eye on the affs, it's virtually impossible to make sure everyone is compliant all the time.
Unfortunately, many players simply don't understand the casino-affiliate relationship. They DO, however, underststand ADVERTISING. They see a banner on an affiliate site which offers the promo, they think this is the SAME as an ADVERT, bought and paid for, but placed by the CASINO for a specified period, and expect that the CASINO would remove the advert when the offer expired simply by NOT asking for another "insertion". They do NOT understand that the site GETS PAID when they click through and deposit, and therefore see no obvious reason for a bad affiliate site to leave up an expired advert that is no longer being paid for.
Casinos, and their affiliate programs, can deal with this by ensuring that expired banners are REMOVED from THEIR servers, and replaced with something more generic. Most affiliate programs give their affiliates code to insert banners into their websites, but many never bother to deactivate old banners when offers in them expire. If the affiliate hasn't noticed the change, and has left the old banners up, the offer is still displayed, despite it being expired.
Where other sites copy the codes, there isn't much the casino, or the program, can do about it, however the codes are then just posted as codes, and do not look like banner ads placed by the casino.
There will always be a number of bad affiliates, who would deliberately set out to mislead, and they might copy the banner onto their own server, so that nothing the casino affiliate program did would prevent them from displaying an expired offer. This type of affiliate is also likely to be promoting "rogue" casinos, since they pay more in commission. Seasoned players can tell the difference, but new ones cannot, and get stung.
The most effective sanction a program has is to close an affiliate account. They stand to lose revenue from EXISTING players, as well as from new ones.
Many players feel there is a "double standard", where an affiliate can misbehave to the level of FRAUD (such as displaying false information/offer codes, or running a covert spamming campaign), yet be given a second chance after a "good talking to", yet a PLAYER who is so much as SUSPECTED of fraud has winnings confiscated, and their account closed, with NO second chances unless they appeal the decision through a third party mediator such as eCogra. Even "play not within the spirit" can result in confiscation of winnings, but an offence of a similar level of severity from an AFFILIATE is treated as a minor issue, with no repercussions.