Making a model or prototype will allow you to get the best way to manufacture the device you have invented. It can be helpful for all sorts of things like figuring out where to put labels, what the shipping weight will probably be, the best way to package it, exactly what it cost to fabricate it, also to get feedback from test users. It is a valuable tool to help you.
If you are going to try to raise money to fabricate the brand new product yourself, or maybe you're demonstrating it with a potential customer to get a big order, you will need the prototype if you do not already have a production unit to exhibit or demonstrate.
People just do not have much imagination. You are an inventor, which means you will have an imagination. Before you can invent something you want the idea...plus it takes imagination to generate new ideas. Others, you will find, simply do do not have the imagination or vision that you just do. Help them.
With an above average prototype or model, your audience needn't come with an imagination. It can make cool product "real" for them, adding tremendously to your credibility. Creating a good prototype can help sell the merchandise even if it isn't even just in production yet.
DON'T delay prototype building until after you file your patent application. You will probably discover flaws or extra features, or discover possible manufacturing problems. With rare exception prototyping is quite worthwhile. You will find more often than not unexpected discoveries from construction of InventHelp prototype.
Testing is very important. A prototype lets you actually test your invention inside a meaningful way. You can test it with individuals besides yourself if appropriate, and you should discover that others will have constructive criticisms and suggestions that might be very valuable.
By searching on the internet you will find model and prototype building companies who can assemble it for you if you don't possess the skills yourself.
There are times when a prototype isn't practical, if it's too expensive as an example, but when it really is possible, I highly recommend an invention prototype or model be produced.