I think Easy CD Creator's popularity has something to do with it's "pretty" and intuitive interface, which some people would even disagree about that. It's definitely tailored to the newbies at burning, which I'm sure is why it is prevalent.
It ships with a LOT of major computer manufacturer's systems; I have 2 old compaqs and 1 gateway that shipped with it. Although, recently my mom bought a compaq and it shipped with RecordNow Max, so maybe Compaq is seeing things a bit differently now.
The reason I don't like it is mainly because of bloat. It takes up way too much hard drive space for my burning needs. Also, it has a slow initialization, which is annoying to me when I need to do a "quick burn".
In the end, though, if it works for you and you see no drawbacks with it, then by all means use it. I prefer burnatonce because it's small (about 3MB), it initializes in a second, and it can burn at my burner's highest speeds without error; it's quick, easy, versatile, and FREE at
www.burnatonce.com