If I forget my smartphone on a train and then some jackass uploads my mp3s on bittorrent, then I will have to face a huge amount of legal trouble, prove my innocence, and possibly be sued for gazillions of dollars.
Call me paranoid but it's simply not worth the risk. True, the likelihood of the above happening is small, but the potential damage if it does happen is huge.
To me, this unlikely risk is not big enough for me to avoid iTunes. In the case of iTunes, it is not trivial for the average user to take your music off an iPhone anyway.
The way I look at it is iTunes scored a serious walloping on the record labels. Have you heard of the not-so-much-paraded feature called "iTunes Match"? iTunes Match is a pay service which makes it even lower on the radar. But I pay for it and consider it a steal ($25/year).
If you turn on iTunes Match, iTunes will scan all your music on your hard drive - including MP3's -
even if they are ripped or pirated - and then iTunes will permanently pretend that you bought that music from iTunes for as long as you subscribe. That enables you to redownload Apple's high-bitrate copy and get all the album art and have it fully sync to all your iTunes-compatible devices, just like you bought it. Although they come as .AAC files, iTunes has a semi-hidden feature that converts it all to MP3 or WAV or other formats, completely in bulk with intact metadata. I don't see Apple as a RIAA pawn.
iTunes Match also lets you copy music from your "collection" over the air (including cellular) on demand to your iPhone, as well as remove it. So if you are walking down the street and want to listen to one of your pirated MP3's you have at home if only it were loaded on your phone, you can download it from iTunes and enjoy it right then and there.
EDIT: I forgot to mention, on all these iTunes downloads there's no DRM. I take that for granted nowadays and didn't even think about it.