Here's the argument.

Niche Agencies thrive because they are less creative and lazy in order to gain easy continual sales because of churn.

The reason the niche agency exists is to make the agency's sales and marketing easier to mass spam one message to one industry so you can scale fast for profits while churning and burning, replacing burnt customers given the bare minimum services and creativity. 

Everything's templatized and the team is rewarded for this consistent mundane following of checklists there is no creative thought or new strategy. Everything is the same for everyone no matter what as they use the same cookie cutter process for one company as they do the next.

Niche agencies survive by doing heavy sales tactics that are hidden under the guise of 'we are experts in this industry this is what we live and breathe'... in reality they care little for the specific industry. The niche then boils down to just being the cow that the agency owner chose to milk (seldom do they have first hand experience in the niche) and the systems and processes (SOPs) they made that the team must follow like a robot.

And it works really well!

It continually brings in new clients constantly paying their high-end, MRR services (2-3k monthly recurring programs to boost the agencies profits), it makes the work easier because its the same day in and day for everyone, no matter what. 

Seldom do these processes change or update unless a major issue occurs as they race to find and fix to run the new version of the process until the next emergency failure.

So the whole point of a "Niche Marketing Agency" is to make sales easy (same conversation, same niche, same tactics for every, single, business. Now doesn't that sound like an awesome creative marketing agency that's going to make YOUR company stand out! -- I didn't think so.

How would I know?

I've worked in web development and marketing since 1999; that's right, back when Yahoo! GeoCities websites were all the rage. We run a white-label marketing agency that provides services and whose clients are made up of mostly Niche Agencies at Growing.Agency, and also a local marketing agency in Miami that manages service-based businesses within the my community called The Marketing Lab; so I do have a lot of experience and skin in the game.

In Conclusion

Niche agencies can be both good and bad. The majority sink into the category of being just a cash cow that the agency owners, typically type-A salesman, milk until it dries up or for the day they sell the marketing agency for another large sum [a means to an end]. 

Find one that is dedicated to your growth and who actually cares. If we've learned anything from recent times, its that the corporations do not have our best interest's in mind and maybe, bigger is indeed not better. 

Will we see a day where the pendulum swings back in favor of supporting small local businesses and back to the age of the "mom and pop"? 

Let's hope so, as corporations continue to reveal they are nothing more than greedy behemoths who treat all underneath a number without human emotion.

That's the spirit that we're helping to fight for, help, and achieve at The Marketing Lab, right here in Miami, FL.