Why certain Themes don't have certain widget options?

Why aren’t some widgets available with certain themes?

if a theme provides some custom widgets or not is the choice of the theme’s developer.

if you are looking for a widget which is not in the default widgets that come with the WordPress installation, search the plugins https://www.ads-software.com/plugins/

so is there a way to add a widget that is not listed with the developer’s theme? I am making a child theme, but I don’t think that changes the widgets that are available.

There are plugins for widgets (as suggested above) – if you’re looking for subscription widget, you might want to use JetPack – it has a widget option.

https://jetpack.me/support/subscriptions/

ok thanks guys. i will check this out and see if it is what i am looking for!