There could be a number of reasons why plumbers may be difficult to find. One reason could be that there is a high demand for their services, and they are all busy with existing projects. Another reason could be that there is a shortage of plumbers in a particular area. Additionally, some plumbers may only work within a certain geographic region, making it harder to find one that is available to work on your specific project.
It could also be the case that the plumber you are looking for is a specialist, and thus hard to find, or that they have a limited availability.
It's also important to consider the time of the year, during peak seasons like summer or winter, plumbers may be more busy than usual, making it harder to schedule an appointment.