As Matt 26z says, there are so many different levels of paysites/programs and each has a different relationship with it's affiliates. Here is my take... and remember, this is only my opinion.

SITES THAT SELL THEMSELVES
For example, sites like Corbin Fisher, Randy Blue, Sean Cody, etc. could probably go on forever without another single affiliate sale and continue to be successfull. They feature outstanding exclusive content that almost sells itself and you can tell a lot of love is poured into these sites. They also have such an incredible presence with their branding. Of course that branding was mostly due to all of the marketing efforts of their affiliates over the years. I would hazard a guess that the majority of their sales now come from type-ins, SE traffic and PPC marketing.
Verdict: Affiliates not necessary

MEGA STRAIGHT PROGRAMS
Then you have the mega-programs with their gay sites like Topbucks, WEG, ARS, etc. that I would guess, rely almost completely on the efforts of their affiliates. They have mostly generic looking sites that NEED strong affiliate marketing to get noticed in the crowded market because their product is substandard. They need to offer every marketing tool available and saturate the market to maintain their high level of sales. And when was the last time you saw a mega-program site with good SEO?
Verdict: Affiliates ABSOLUTELY necessary

MEGA GAY PROGRAMS
This category of sponsor programs include programs like Pridebucks, Gunzblazing, Intense Cash, etc. And they take their main cue from the Mega Straight Programs. They offer a large variety of affiliate marketing tools BUT generally have excellent quality content. Affiliate support is usually needed for these programs because their branding and/or SEO is often not as strong as the "Sites That Sell Themselves". Broke Straight Boys (from Intense Cash) is probably the only site in this category that would fit comfortably in the "Sites that Sell Themselves".
Verdict: Affiliates necessary

THE UP-AND-COMERS
Sites like Blake Mason, Chaos Men, Buzz West, (dare I say) UK Naked Men, etc. try to model themselves after the "Sites That Sell Themselves". And despite the high level of their content and efforts at branding, just aren't quite there yet. Often, they only have the one site in their portfolio and are very passionate about their baby. These guys often try harder with their SEO and self-marketing. The usually offer some affiliate tools but don't focus real hard on them... yet. Perhaps, because they have managed to slip under the radar of the "whales". Once the whales catch their scent and demand the whole plethora of sophisticated marketing tools so they can send dozens of sales per day, then the "Up And Comers" may become more advanced with their use of marketing tools. Or perhaps they will just continue to steadily build their membership base themselves and one day move up into the big leagues. But these are often the sites that will sell best for smaller affiliates who are willing to work a little harder by building their own galleries, etc. because their affiliate marketing tools haven't saturated the market... yet.
Verdict: Affiliates optional for site owner. Self-marketing and SEO often shows better returns

THE SCRAPPY SITES
These are usually fetish sites or sites started by newbies that have no clue. They are often processed by Verotel or some other even-less reputable processor. Updates are usually infrequent. The tours are usually VERY amateur looking and minimal. They don't appeal to a broad audience but often convert like CRAZY with the right kind of traffic.
Verdict: Sometimes they don't even have affiliate programs and when they do, may have multiple processors on the join page. But these sites can be unpolished gems for affiliates who can send the right kind of traffic.