advice
is the better with affiliate network
if you want you can try direct affiliation.

Advertisers mostly go to CPA Networks as thats much easy option for them :|

I dont think advertisers have their own affiliate program :/

Direct advertisers don't like using individual affiliates since they usually have no recourse if there is a major problem or a legal issue (chances are, you can't get anything out of suing a single person so if they damage you, you're stuck as an advertiser).

Instead, they work with established networks. Its not only easier in terms of consolidating their touch points (having to deal with many people means more staff, more tracking etc) but there is also the legal side of things. Its also easier to research a networks history where as with a person, you are putting your inventory in their hands.

What we do at our network is run many ads from exclusive advertisers who we've gained the trust of over the years and we mix in our own in house ads since we have a direct pipeline to Affiliates. Its a hybrid approach as we're able to be both the advertiser and the network.

I hope that helps give you some perspective on why things are the way they are.

Peter