Magento 2.3 - What is mean composer.json on Module Development?

I have created module without conposer.json and my module working good,

Module Structure :

What are all the disadvantages of creating module without composer.json?

composer.json makes the module installable via Composer.
Also, Magento expects the composer.json file existance in some rare scenarios (e.g. \Magento\Framework\Module\Dir\Reader::getComposerJsonFiles()), and the module will fail without the file.

@dmitrii_fediuk Added composer.json after created module is it possible to uninstall the module using composer? my module => https://github.com/ZusZus/simple-module/tree/master/app/code/Gta/Mymod