Making a model or prototype can help you get the best approach to manufacture the device you've got invented. It can be helpful for all kinds of things like determining where you can put labels, exactly what the shipping weight will be, the proper way to package it, exactly what it might cost to fabricate it, also to get feedback from test users. It's a valuable tool to work with.
If you are going to try to raise money to produce the new product yourself, or if you're demonstrating it to some potential customer to get a big order, you will need the prototype if you do not curently have a production unit to demonstrate or demonstrate.
People just don't have much imagination. You are an inventor, which means you will have an imagination. Before you invent something want the idea...plus it takes imagination to generate new ideas. Others, you will discover, simply do not have the imagination or vision that you simply do. Help them out.
With an above average prototype or model, your audience needn't provide an imagination. It can make new service "real" for the kids, adding tremendously in your credibility. Having a good prototype can help sell the product even if it is not even in production yet.
DON'T put off prototype building until once you file your patent application. You'll likely discover flaws or new features, or discover possible manufacturing problems. With rare exception prototyping is very worthwhile. You can find more often than not unexpected discoveries from construction of InventHelp invention prototypes.
Exams are essential. A prototype allows you to actually test your invention in the meaningful way. You can look at it with people besides yourself if appropriate, and you should find that other folks will have constructive criticisms and suggestions that might be very valuable.
By doing a search online you will find model and prototype building companies who are able to build it to suit your needs if you don't hold the skills yourself.
Sure there are times when a prototype just isn't practical, if it is too costly as an example, but when it really is possible, I highly recommend an invention prototype or model be generated.