Ineligible songs will not convert to ACC as they are protected

From About iCloud Music Library icons and status - Apple Support:

Ineligible: Your computer isn't authorized to play this song or the file type can't be added to iCloud Music Library. A song might be ineligible if it wasn't purchased from the iTunes Store or was purchased using a different Apple ID, or if the song file is larger than 200 MB, is longer than two hours, or was encoded at 96 Kbps or less.

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Yes, protected tracks purchased from the iTunes Store can not be converted in this way. However, you can burn them to an Audio CD then re-import them.

Just because you can play a protected track doesn't mean that the track is yours as you may only have authorisation to play.

Although yes, iTunes Match can be a bit of pain if you have content coming from more than the one iTune account. For instance, I have a account in 2 different countries and as iTunes doesn't allow a unified account I can only use iTunes Match for part of my purchasing. Granted most content comes DRM-free it's still a pain.

What do you mean? Are you refering to the fact the track is "ineligible?" See this Apple KB article for help in understand why certain tracks may be "ineligible." In particular, pay attention to this note:

A song will not be uploaded to iCloud if the song contains DRM, was purchased using a different Apple ID, and could not be matched.

http://support.apple.com/kb/TS4054?viewlocale=en_US&locale=en_US

Why?