Was there a time before bike trends? I never noticed them until the 2000's. I thought that a bike is a bike is a bike. When it's got 21 gears, it's a fancy bike. However, now judging by the variety of so many different retro bikes, other people must have thought differently. Anyways, the first trend that I remember started from a music video. I don't remember what the band was or when it was shot. It must have been in the beginning of the last decade. It was a retro music video. A bunch of boys were riding their cruiser bikes on a hot summer road. The next summer cruisers were everywhere, and apparently they did come to stay, because they are still everywhere.
The next trend was Jopo. Do you have them in your country? There has been a Jopo trend before, about 40 years ago. A fiancé of my friend told me that he has an old Jopo somewhere, not one of those modern cheap china copies. He is planning to restore it into usable condition in the spring and, if it is ready in time, he has promised to lend it to Anna when she finds her way to Finland in the early summer (YAY)! I have never tried a Jopo. The trend of the next summer has been predicted to be Poni (=pony), which looks exactly like Jopo to me, apart from the text on its frame. There's also an overlapping eternal granny bike trend. Women love them. My bike is a granny bike, or a classic, one might say. In addition to Jopos and grannies, fancy paintwork seems to be in fashion too.
Flower power on a modern cruiser
Well, fashion changes. People do too. If you get tired of your old outdated bike, please, give it to someone or sell it at a flee market. Or give it to charity, e.g. send it to Africa. There is a home somewhere for the old bike too. Usable bikes don't belong into the dump, no matter what the fashion says.