A broadly written patent application can give the patent owner broad patent protection. This can equate to the patent owner being able to stop more knockoffs and copycats.
Some patent owners, in a quest to prevent knockoffs, will sometimes make the patent application vague. The hope is that a vague patent description will make it harder for someone to copy the invention.
And in some instances, patent owners will seek to omit (or just provide partial descriptions of) trade secrets that are needed to make the invention. Again, the hope is that the omission will make it harder for others to knockoff the invention.
However, the patent laws place a limit on the breadth and vagueness of a patent application.
First, the patent laws require that the written description of the invention be in "full, clear, concise, and exact terms." That, of course, is open to interpretation and argument. But that is the standard by which the patent office or judge will determine if the patent satisfies the patent laws. If not satisfied, the patent will be invalid. And an invalid patent allows others to copy the invention.
Second, the patent laws require that the written description "enable [one] to make and use [the invention]". In other words, the written description should not require "undue experimentation" to make the invention. Again, this requirement is open to interpretation and argument. But if not met, the patent will be invalid.
Here is an additional limitation or barrier to a broad patent application. The broader the description, the greater likelihood that "prior art" can invalidate the patent.
For example, assume a broad patent covered a "chair", and a narrower patent covered a "chair with 8 legs". There would likely be more "prior art" for a "chair" as opposed to a "chair with 8 legs." If there is more prior art, there is a greater chance that the prior art would invalidate the patent.
WHAT CAN YOU DO?
There will always be a trade-off between obtaining the broadest patent and writing the patent application so that it avoids prior art.
Often, it is a better practice to write the patent with a clear focus on your invention - e.g., the addition of 8 legs to a chair - instead of the broader concept of simply a chair.