disable checkout in Magento 2 can be helpful when you want to allow customers to browse the site, check the products and its prices, add them to cart but restrict the checkout and place an order. You can have your own reasons to do so, be it issues in the inventory of products or shipping, etc. Also, if your product is still in the testing stage and you only want your customers to check demo but not yet purchase it, you can disable checkout. Or, if you opt for any third party checkout solutions for Magento 2 store, disabling the default Magento 2 one page checkout makes sense. Whatever it is, disabling checkout in Magento 2 is easy as shown here:
Steps to Disable Checkout in Magento 2:

- Login to Magento 2 admin panel
- Navigate to Stores > Settings > Configuration
- Under Sales, select Checkout
- Expand Checkout Options section
- Set No in the Enable Onepage Checkout field to disable the checkout for existing customers.
- Click Save Config button