The description contains HTML markup, such as <p></p> for paragraph breaks. CDATA is a nice and clean way to encode them without breaking anything.
The title doesn't contain any markup, and shouldn't. A good old escape function covers both the "doesn't" part and the "shouldn't" part.
I see people stuffing all sorts of HTML tags and nonstandard attributes in an RSS <description>, just because CDATA allows them to do so without breaking the parser. Images, videos, inline SVGs with maybe some scripts inside...
The RSS spec should never have allowed this. Reading a feed would have been much more pleasant (not to mention safer for everyone!) if the contents were required to be in plain text.
At least with a cdata tag your being explicitly told “here be dragons”