It must have been a short lived phase, because I don't remember these t-shirts being popular much past one or two years. My family doesn't even remember me having this t-shirt. The only photos I could find of these shirts is an ad for other rainbow, glitter t-shirts offering a "Tonight's the Night" t-shirt (I rather have a "Do You Think I'm Sexy" t-shirt myself) and a vintage t-shirt on E-bay that sports the title, "Dancing Machine." I mentioned this to some co-workers and they didn't remember this fad either. However, it has stuck with me since childhood.
I think what strikes me about his now is how goofy this was. It almost makes no sense to wear a song title on your shirt, because if the person isn't familiar with the song it seems like a random, off-the-wall statement. Why would I say this? Because I know from experience. As I mentioned above, the t-shirt I had said "New Kid In Town." I had older people and redneck types in Lebanon say things to me like, "Git that shirt off! You ain't no new kid it town!" Not wanting to open up some typical Ozarker "That-is-what-is-wrong-with-our-country-it-going-to-Hell-in-a-handbag" discussion, but there is a delightful awkwardness about a seven or eight year old girl wearing a t-shirt that says "Afternoon Delight" or "Undercover Angel."
I think I know a little bit of the reasoning behind these t-shirts. Rainbow, glitter graphics on t-shirts was the new hot thing in the late 70s, as mentioned in the above t-shirt ad. I'm guessing the graphics were limited in the way they could be used, so they either had to be a small, simple picture or words.
Why just song title? My guess is that a t-shirt manufacture could get away with just the song title, where as band's names would require permission and probably a hefty licensing fee. Also bands in that era had special logos, which might not work with the rainbow, glitter graphics. Note that in the ads above, the company is selling shirts that say "Eagles" and "Kiss," but it is not there usual logos. I don't believe the "Angel" and "Rainbow" t-shirts have anything to do with the heavy metal bands Angel and Rainbow, it is just coincidence. Matter of fact, if you look closely, it is just the words "Eagles" and "Kiss." Sneaky, huh?
I was beginning to wonder if these t-shirts were just in my imagination. I looked through old magazines and comic books for photos or ads for these t-shirts. I looked on the Internet for photos of them. Sadly, I discoverred some very disgusting racist t-shirts being sold on-line (Klanwear?). Finally, found the pictures I used above. So my reasoning is this trend didn't go over. Maybe everyone was like me and realized it was kind of goofy.