In recent months, the question of whether WordPress should convert uploaded JPEG files to WebP files by default has often been raised in the WordPress developer community. Thoughts went so far that this feature should be implemented by default in WordPress 6.0. 
WordPress 6.0 should integrate WebP even more strongly
However, the proposal was rejected rather quickly.
With the upcoming WordPress version 6.1, however, the question resurfaced, and now Matt Mullenweg seems to have put his foot down:
I went through all the conversations and issues here. I’m interested in supporting new formats and improving performance, but I think this change sent to users by default when upgrading to 6.1 is too much for now, especially because of operating systems’ clunky interactions with webp (and HEIC!) files.
I am glad that support for webp and HEIC files remains in the core, as we should be generous in what we accept and work with, but not with the change to convert everything to webp when JPEGs are uploaded.
This is excellent territory for a plugin that is the norm, a concept that I think every Make team should explore much more as a place to experiment and add functionality, just as we have done in the past with MP6 and Gutenberg. I think the plugin directory needs more collaborative, community developed and non-commercial or no-upgrade plugins that do something right, and Make-teams are the perfect groups to develop and maintain those. It is the ethos and process of the core that is applied to plugins so that we can officially recommend them and present them in the plugin directory, and that also gives us time to mature the environment around something (like WebP). Source : https://make.wordpress.org/core/2022/09/11/webp-in-core-for-6-1/
Matt Mullenweg suggests instead making the functionality of automatically converting JPEG images to WebP available with a plugin, as was the case for Gutenberg before its implementation in WordPress core.
General support for the WebP format remains, of course. This has been around since WordPress 5.8: WebP will soon make WordPress even faster
At the same time, Matt Mullenweg points out the importance and significance of plugins in general in another article. He also discusses how WordPress development teams can develop new features with less pressure but with less revision effort by taking a plugin-first approach. And he immediately gives some ideas on how to do this.
