how can race fans support a railroad?
Norfolk Southern might come into NASCAR for several reasons. First is B to B...there are a lot of sponsors (like a few listed earlier, CAT, Cessna etc) whose only purpose in NASCAR is to entertain giant clients. The access you get as a primary is one of the biggest perks, and I've seen giant deals take place at the track simply because the potential client was having an awesome time. All the CAT people do week in and week out is entertain their big fish, or potential big fish. If they make a sale or two here or there because NASCAR fans see it and happen to need heavy machinery, that's more gravy than meat.
Second reason might be safety messaging. CSX has been in the sport a couple of years, and are currently with the #34. There's a yellow bumper sticker on the back of David's car each week that says "I brake for trains." It's part of their Play It Safe campaign, which was also on David's car at the All Star race (hood said "beats Goliath, brakes for trains). NS might be spending huge money to get exposure, and simply relying on the fact that it's Jr. CSX spends a ton less, and mostly does "stunts" to get the word out. CSX also had a primary at Richmond this year, and fans were all asked to sign David's hood promising to brake for trains. That initiative received a lot of press, including a big picture of the hood in USA Today. There's plenty of ways to get a message out using NASCAR - spending mad cash on Jr is certainly one of them.
They might also be using NASCAR for internal purposes. Entertaining employees, rewarding employees, employee moral (it would be nice to work for a company who shows up on the most popular driver in NASCAR's car...then again, I might be pissed if I didn't get a good raise, but Jr got millions...who the heck knows) a perk for landing high level talent, etc...
So aside from "here's my product, go buy it" NASCAR really does offer sponsors a lot of positive business opportunity. It's not much different (other than price, obviously) than companies buying season tickets/suites to sporting events, or vacation homes for employee/customer use etc. A lot of deals go down in that garage.