First off, let's be clear about one thing: I love Johnny Cash. I've always been a big fan of his music and his style. I use the "Man in Black" title sarcastically and with no disrespect intended.
Why is it that something like 90% of motorcycle gear is black? I've been asking myself this question for a few years now and I can't seem to figure it out. Is there a safety advantage? Obviously not, as it's probably the most inconspicuous of colours. What about practicality? Nada. Have you ever been stuck in gridlock under the mid-August sun while wearing a black riding jacket? Fun, eh?
My favourite long-distance riding jacket right now is a First Gear Kathmandu that I picked-up last year at a considerable discount over at New Enough (now motorcyclegear.com - as a sidebar, those guys are great to deal with, I highly recommend buying your gear there). It's a great jacket, with plenty of pockets, good venting, CE armour in the right places, and hey - it's even got a hydrapack pocket so you can maintain your H2O levels while riding. Best of all: it's beige! Yup, that's right, beige. Plain, simple, boring, beige. The light colour helps reflect way more heat from the sun's rays than any of my black riding jackets. I liked it so much that two weeks later I ordered the matching pants (again - at a considerable discount).
SWMBO also liked my new jacket. So much that I had to order a Kilimanjaro for her in the same boring beige. She loved the jacket and, naturally, wanted the matching pants. Uh oh! No such thing. I've searched and searched the web, googling 'til the wee hours of the morning. No dime. It's near impossible to find some nice, beige, ladies' riding pants. Go figure?
Sure, a two-piece touring suit is a bit bulkier and slower to get in and out of than, say a Roadcrafter. But the 'Stich is in dire need of a makeover. Sure, it's got the quality and practicality down, but it's about as fashionable as a hazmat suit.
Which may be the main reason why so many riding jackets & pants are black. Maybe it's a fashion thing? The idea of black leather and motorbikes has so deeply ingrained itself into the whole "biker culture" thing that many people wouldn't consider wearing any other colour... Except for the racer boys who look like Sherwin Williams did a number on their puck-kneed suits. But that's another story...