This is an opportunity to guide people through the process of structuring the app so they can plan what should be on each page. It’s also a tool that can be used to illustrate funnels and landing pages.
Keep in mind that one who is more experienced, might simply want to code the app up sticking to something like Bootstraps fundamentals. Coding up could be quicker in the short term but I feel like there is some value to be had in mapping things out be fore you build things in code.
Here is a wireframe taken from Root. Root is a template I bought for Figma which allows me to create my wireframes in Figma now, rather than Balsamiq. In theory, Figma should be more robust, but it’s a very young app. To be honest Balsmiq has been one of the buggiest apps I have ever used, pretty consistently too.