That problem is a bit in line with coaches and courses. Why does someone sell a course with the content “how to get rich”, if they could use it for their own gain? Most of the time the answer is because they are not competent enough to make it in the private field on themself, but have acquired some knowledge in the field that they want to salvage.
Most average agencies do not provide any value. They just make the customer think the marketing problem is being taken care of. For example, if a possible client wants to start working with you and they tell you “Hey, I want more followers” and you don’t ask them what they need those followers for, you probably not doing a good job for the client. Most of those people don’t know how to achieve the goals they set themself (if its an “influencer”) or are a local business company without a marketing department.
Early in my stage of Internet Marketing, I attended meetings with some big companies that hired our team for taking care of their web presence, which is still today an efficient way to get your foot into the door, but we were never able to get passed their existing marketing department efficiently. They made really bad choices both on the requirements they put on us and on any possible improvements we could have made.
So as an agency you will see a bit mix of everything out there until you decide what you want to do. Especially what you enjoy doing. Sitting in a room with 6 marketing department dummies and their post-it’s trying to fix their never-ending bad choices was not my pick. After that specific contract ended, I tried to only work with “companies” where I can have a private talk with the person in charge of the company if needed. Especially if their marketing department is making a fool of the company head (by going in a provable wrong direction).
To answer your question a bit more specific. Did you ever try to get your hand on an “expert” in the Internet Marketing field? I mean a real expert. Not that kind of coaching/consulting nonsense. People that push crazy ROI’s on ad budget are like a gold mine. Especially when it comes to eCommerce you can just pump all that ad budget right back into the ad account after the sales. So there is basically (assuming you have enough funding to fill the gaps of money being transferred from one payment processor to another) no limit of ad spend until you completely run out of demographics or accept a much lower ROI.