Hello,

Many of our customers were complaining about their disk size being filled up and this is why we removed the default medium size which we generate to avoid disk space being filled up when users try to upload large images.

You should have left the medium image size as an option. If the user does not need the medium size, he can turn it off.
But trust me, Google has made it clear that images need to be optimized.
And when you load a 1200x800 image on a page and display it at 600x400, that's VERY bad.
This greatly slows down page loading speed, and Google PageSpeed Insights will always give small points for your site.
It's very, very bad for SEO.

Thanks for the input. Will consider to see if we could add such a settings but I do not think that having 600x400 is going to cut it with responsive designs these days. Monitors are getting larger and you also need to consider sites that uses responsive layouts.

This was one of the reasons why we decided to take off the medium variation.