They Take 50% On Average
Agencies take creators' hard earned money and have the power to make decisions about their content. Most of these agencies are taking 50% or more of their earnings, while OnlyFans still takes 20%. I don't want some guy making that much money off of my porn videos that I spend all my time writing, filming, and editing. Also, I would have to give this agency full access to my account and content. I have heard horror stories where there was a falling out between the model and her agency and they unfortunately messaged all her fans some insane messages making them leave her page.
They Scam Fans
Agencies use scam tactics to suck money from your fanbase. I prefer to keep my OnlyFans page genuine even while still trying to sell to my fans and make money. I don't use tricks or lies to make money, I just provide high value videos and services that people feel good about spending money on. A lot of agencies will use bizarre scammy sales tactics like lying about 'first person to tip $X gets to see this' when obviously anyone who tips will see it. They will exaggerate or lie about what they are trying to sell while charging high prices. They will also basically beg for money from your fans and be hostile or rude to them if they don't spend hundreds of dollars. Meanwhile I am understanding of people's financial situations and appreciate the money and support I get for providing good content. Sometimes agencies will even engage in romance scam tactics like alluding to meeting up with your fans which can become extremely dangerous for the model, especially once the fan finds out it was a scam.
They Manipulate Other Content Creators
Agencies prey on other content creators, women mostly. Some will try to recruit women who don't even have an OnlyFans or make adult content. I get DMs on Instagram all the time from other (much more famous) pornstar and OnlyFans model accounts which are so obviously run by their agencies. You can tell which ones have the same agency because they will use the same opener when they message you lmao. The agency pretends they are the creator messaging me and try to compliment me and befriend me. It's never upfront and it's very shady and annoying. I fell for it a few times, thinking some of them actually wanted to be my friend, until I learned this is what they all do. Eventually they will ask if I have an agency and if not they can put me in contact with theirs. All the while it's really just the agency messaging me and using shady tactics to get genuine female creators baited into talking to them.
Obviously, a lot of OnlyFans creators do use agencies and I think it's pretty easy to spot them. I try not to judge how other women choose to run their adult content careers, and I do feel like some of them are being tricked into joining an agency since they will just do everything for them. But ultimately, I really just prefer and enjoy doing everything on my own and actually getting to know my fans and talking with them.