Many woocommerce stores do not take payments online or here are some woocommerce stores which provide free products, Free Membership, Free Digital Goods etc. such stores do not need payment gateways.
In this video tutorial we can see how a single line of code specifically a filter can help us to disable all payment gateways.
Here is code snippet to add in you child theme’s functions.php file
// Disable all payment gateways on the checkout page
add_filter( 'woocommerce_cart_needs_payment', '__return_false' );