Why isn't MTV selling truetones?

I thought I'd take a look at MTV today as one of my clients is interested in advertising there next year. Of course, I couldn't resist but take a look at their mobile ringtone offering and was surprised to see that they're *not* selling truetones (with the exception of 'pimp my ride'). The Music Solution seems to do all their ringtones and I just wondered why they hadn't got round to doing the real music? Seems a bit backward to me - especially when they're already playing around with mobile content with Motorola and made-for- mobile video which is much more complex than ringtones. Anyone know the answer? Is it a DRM issue?