The Obvious Reasons
1) Sound Quality. This is an accurate answer if you have crisp, mint vinyl, but a wildly inaccurate answer if you have scratched up, crackly, popping vinyl. On the other hand, if you have a scratched CD, it will go "wubwubwubwubwubwubwubwubwubwubwubwubwubwubwub" until you turn it off and throw it away. The first time I heard a scratched CD, it was something my dad had left on when he left the house and I thought we had a poltergeist. LP's just sound like Rice Krispies when they get scuffed (well, up to a certain point).
2) I am pretentious. I do my best to contain it, I try not to look down on people who like stuff that I don't (hey, I've got plenty of musical skeletons in my closet too) but when I'm honest with myself, it's true. I think the stuff I'm into is the best stuff to be into. I grew up with cassettes and CD's, so I will confess that when I switched to vinyl, part of the reason was that there was a mystique about it: it was my way of connecting with the history of all the music that I missed. I'm sorry, I can't help it. Sue me. But that was then. I now have better reasons.
Practical and Semi-Accurate
3) Cost. I can walk into Laurie's Planet of Sound with fifteen dollars in my pocket and pick up one new CD by the Who, or four of their albums in pretty awesome condition. There are the collector's market LP's which will be more expensive than their still-in-print CD counterparts, and there are certain major labels who are still trying to rape people on the cost of LP's (remember how the last White Stripes LP was like $30? Yeah.) But on average you can pick up LP's on the cheap. Indie labels generally price new records about the same as the CD's, and many of them will give you a code so you can download the album in mp3 format legally from their website so you can listen to it on your iPod.
Sentimental, but honestly, these are my real reasons:
4) The Hunt. There is an art to getting really involved in buying used LP's. It's rare that you can walk into a record store looking for a specific album and rely on it being there. It's more of a hunt-and-see-what's-there process. This ends up leading to some disappointments when you strike out, and it leads to some days when you spend way more than you were planning on spending, but what it generally leads to is being caught off-guard and usually being very pleasantly surprised by what you end up getting, which to me is part of the appeal.
4a) Every piece of vinyl is unique. When I first started buying LP's, I knew I was going to want a copy of Blood on the Tracks, but I passed over about five copies because I knew that on that particular record, I didn't want to screw around with copies that were anything less than spotless. Every LP goes on its own journey: sometimes they're hermetically sealed in five layers of plastic, sometimes they're stored in a stack in someone's flood-prone basement. Sometimes they're placed on the turntable gingerly touching only the label and the wax, some are owned by people with under-supervised toddlers or a cat who likes to bat around the needle while the record is playing. Finding A copy of a record is one thing; finding YOUR copy is another.
5) Presence. With records, I can see where the needle is when the track is playing, I can see where each imperfection is, I can run my fingers over scratches to tell if they'll be audible, I can have a good idea how the process of playing the thing works without understanding binary code. CD's play in a closed space, out of sight and out of contact with the listener. Music should be a physical presence, whether it's live or recorded. More importantly, LP's are more physically substantial. They are heavier, more unwieldy, and they just take up way more space than CD's. But that's the point. I was flipping through the booklet for the brand shiny new Mission of Burma reissues, which have old band photos fliers, and I realized how different it would look if I had gotten the CD version. To put it in perspective, let's look at one of my favorite album covers:
A CD jewel case booklet is about 40% of both horizontal and vertical dimensions of an LP cover (that's about 17% of the total area). When you take it down proportionally (from that already too-small image) you get this:
The smaller Lung Leg gets, the less threatening she is when she's snarling at you. A CD cover is a thumbnail image of the real piece of art that an LP cover should be.
Which is really the crux of the argument. An album should be a pretty comprehensive sensory experience. You can listen to the music, you can feel the grooves under your fingertips, you have an image to examine clearly. I'm all for the portability of mp3's, and the digitization of music has enriched my life, to be sure. But having a file on your iPod and having a record is like saying you're going to throw out your easy chair and replace it with the seat from an old Honda. Mp3's are for making you more comfortable in transit, LP's are for actually having something real. CD's exist in the ether between the two, taking up too much physical space without giving you any real physical interaction. Hence, I'll take the vinyl.