Most themes I’ve seen don’t have a recent posts widget with images, unless it’s one of those overly bloated themeforest themes (yuck).
The whole point of GeneratePress is that it’s a lightweight theme, with only the essentials. Then, as a user, you can extend it to include only the things you need and want.
There’s actually very little difference between you adding a plugin with this functionality and me adding the code into the theme. The only place you will see any difference is on the “Plugins” page, which takes a little longer to load with a lot of plugins since they have to check for updates.
This plugin does way more than I would ever consider adding into the theme: https://wordpress.org/plugins/recent-posts-widget-extended/ – why use another theme which wouldn’t have the options included in this plugin, just to have images in your recent posts widget? Seems like adding the plugin is a way better solution – in my opinion at least.
That’s not to say I’ll never add functionality like this, but at this time, I don’t really see the point. As a user, I would rather use a plugin being focused on by a plugin author than have a theme developer (who has to focus on all aspects of the theme, and add-ons) add it and forget about it.
Hopefully this kind of explains my stance on it – I use to have another theme which was bloated with custom widgets and all kinds of other stuff. I want to make sure GP stays lightweight and extendable.