The design patterns of emails and landing pages is substantially distinct.
Landing Pages can contain elements such as JavaScript and global CSS to landing pages. Most elements "float" in the layout.
Most email clients do not support JavaScript and the one that does (Mozilla Thunderbird) sets to disabled by default.
Emails use in-line styles rather than global CSS. The layout is mostly governed by tables.
The functionalities in Design Studio tend to reflect the fundamental differences between emails and landing pages.