I understand that you don't need a working model to be granted a patent in the USA, but you do in the UK, and probably Europe.
It makes sense to need a model, otherwise someone can patent an idea and just sit on it, preventing anyone else from using it.
There's a common trope in cartoons, etc., concerning inventors having to produce and submit (typically miniature) models of an invention as a requirement of the patent application process.
Generally speaking, this isn't true ...
It is true that the US Patent Office originally required a miniature model of mechanical inventions to be submitted in support of a patent application. This requirement was abolished almost 140 years ago (1880).
Current US and UK patent regulations require a detailed description of the thing being patented. This description is prescribed to extend only as far as a sufficiently detailed text and drawings / illustrations sufficient to support the textual description.
Off hand, I don't know of any nation that currently requires a physical model to be submitted in support of a patent application. For that matter, I'm not sure how many (if any) nations other than the USA ever imposed such a requirement.
Patents are issued on the basis of originality and a sufficiently detailed description establishing the bounds of the patent's applicability. Feasibility, economic viability, practicality, etc., are factors that might facilitate acceptance of the application, but they aren't factors required to approve the application.
Of course, if this happened, then the patentee could claim royalties for something he/she only thought of, but never knew how to develop.
There's a common misconception about what legal effect a patent has. A patent does not automatically grant any actionable license to exclusively market or profit from an invention. It simply certifies that the patentee is accorded intellectual property rights which can be leveraged to limit or prevent others in using, marketing, and / or profiting from the patented item. It's up to the patentee to act (or not) if someone else employs something for which he / she holds patent rights.
A patent is in effect a form of property ownership. Holding the deed to your land doesn't automatically mean nobody else can walk across it. It does, however, afford you the right to act so as to prohibit / inhibit / prevent trespassing. If you take no such action, there's no basis for prosecuting anyone who walks across your land.
As a result, obtaining a patent allows the patentee rights via which others can be prevented from locking away an invention for their own purposes or gain. This preventative angle is just as valid and important a motivation for seeking patents as facilitating the patentee's own gains.