Agents don't always drop their actors, sometimes it's the other way around - the actor will drop the agent,
This can happen for various reasons. One reason is because they believe the grass is greener on the other side.
As an actor, I hear a lot of conversation of actors comparing notes on how many auditions they're going to, how many contacts they've made, how many bookings they've made and some of the actors in the discussion put on a brave face whilst internally start counting in their heads how many mentioned they DIDN'T get or have.
They then start this thought process of "maybe I should move to another agency"? And they start their "research" and in two months, they've dropped their agent and moved on to a new one and have to start from square one.
The problem with this is that the grass is only greener where you water it, and if you don't water it, you'll reap the benefits of what you sow. In order to stop this from happening to you, there's a few things to think about:
TIME
Our industry takes time for people to get to know who you are, what your work is like and who you're represented by. What are you doing to quicken this pace? Are you attending auditions for student films, shorts or web series? Are you attending industry events? Are you going to class and workshops?
RELATIONSHIPS
Our industry is all about relationships. That's why you have an agent to begin with - to utilise their network because you don't have one to begin with. Why don't you start growing yours because you have one too - everyone you went to acting school with could be a future celebrity, agent, producer, director, etc so foster those relationships. Every time you go to an acting class, your fellow classmates and teachers are now part of your network. Everytime you go to an industry event, you have the potential to meet industry people. I've even met industry people at social parties who was a friend of a friend, I met a director when I helped a friend self tape, I've met a producer on set while I was an extra - all of which has resulted in work.
SUBMISSION REPORT
Have you asked your agent for your submission report? When you do, it may reveal that your agent has indeed been doing their job in submitting you however casting just isn't taking the bite. This could mean you're not in the market at the moment.
The point is, if you don't allow yourself the time to go oat your pace for your career, then you're always going to be unhappy. You need to compare yourself to where you were a month ago, six months ago, 12 months ago, even 24 months ago and you'll realise you've been going at the pace that is best for you.
If you do drop your agent, you'll be starting from square one with a new agent and that in itself will take time for them to get to know you and build that relationship.
CHECKLIST:
Evaluate your career with your past.
Utilise your network.
Give yourself more time.
Stop being impatient. You've got more time than you think.
Look through your submission report.
Foster your relationship with your agent