Ir you want your structured data to appear in Google's rich snippets or knowledge boxes, you must follow their guidelines. You can have a better click-through rate as searchers see exactly what your web page is about. This can lead to higher rankings as you're providing a better user experience.
Google has to understand the data, as do people, do schema.org vocabulary and JSON-LD is usually the standard implementation to help search engines understand your content. Even if your data is marked up correctly, there's no guarantee your data will appear in the search results. Their results depend on what they believe is best for the user considering their intent.
Use Google’s Structured Data Markup Helper to help you get started with structured data markup for book reviews, local businesses, recipes, products and more. You can test your code and see what it will look like if Google shows it in the search results. It's usually possible to add structured data to your website, even with limited back-end experience. If you're lost, a developer can help you implement structured data.
Using structured data with schema.org is good for SEO, including voice search optimization. Amazon schema markup data for local business intent. Despite numerous brand's success with structured data, only a small percentage of brands use it. They don't know about it, don't understand it or their content management system does not support it.
Since they are SEO benefits to using structured data markup, there are black hatters ready to abuse it, including people using structured data not relevant to the main content of the web page. Google won't display inaccurate structured data and they may flag it as spam. It isn't the most common black hat method yet, but more people will use it as structured data increases in popularity. For more information click here https://www.reddit.com/r/SEO/comments/czgks2/ishowtostructureddatarightforyourkindof/.