Why does `Podfile.lock` change `SPEC CHECKSUMS` section on `pod install` when nothing has changed?

Question

I don't check in my Pods dir into source control.

If I run pod install, touch nothing, and then run pod install a few minutes later the SPEC CHECKSUMS section of my Podfile.lock changes.

Why?

pod --version
1.9.3

"react-native": "0.63.2",

Podfile:

require_relative '../node_modules/@react-native-community/cli-platform-ios/native_modules'
require_relative '../node_modules/react-native/scripts/react_native_pods'

platform :ios, '11.0'

target 'Myapp' do
  config = use_native_modules!

  use_react_native!(:path => config["reactNativePath"])
end