When I advertise Aikido, I don't get much response from the community, but advertising the "self-defense" class has already had a better response.
I think you make an interesting point, Chris. Not every potential aikidoka wants to wear a gi, bow or learn a foreign language. We never bothered with workout costumes when I studied CMA and, if I'm honest, I've never been comfortable in my hakama. It's just not a good look for me. I suspect that the millennial generation (who make up the core of our potential newbies now) are even less impressed with the costume than I am. I'm not sure that aikido without gis is the answer to dwindling class sizes but it's something to think about.
A friend once recounted a story about coming out of a karate class at the YMCA and hearing some guy yell, "Look at the (pansy) in his pajamas!" My friend turned around ready to return the insult but thought better of it when he saw the guy was about twice his size. The gi and all the culture that come with learning the art are simply not held in esteem by many people.
Coincidentally, I was at a seminar this last weekend where everyone wore sweats. It brought a welcome informality to the experience and helped bring focus to the material at hand. This in contrast to what I've come to expect when I enter a dojo. There always seems to be just a little bit of ego introduced when budo people gear up; which is odd when you consider that gis are essentially just underwear.