I don't read a ton of manga anymore, and those I do read are mostly series that are only out in Japan, so I end up having to read them online for lack of being able to any other way. :/
Though, when I really like a series, I will buy the manga themselves. I used to buy 'em on a whim, just to own a new manga, but that was back when I was in middle school, and highschool and read them often. Now days I have to really love a series to bother actually buying it, and I know that's bad of me. xD;
It's more of a "I could sit in my room for hours, and read manga, or I do other things that I would enjoy more / need to get done", so lack of time plays a part.