They can help you move
I’m not crazy and I’m not making this up. There are several moving companies around the world that use cargo bikes and trailer-like attachments for bikes to help people move all their furniture relatively hassle-free. And these aren’t just based in bicycle cities either; there’s one in Montreal for example, and another in Sweden.
As for the why: while it’ll take more than one bike, it’s cheaper than renting a truck. The cyclists for these companies have the equipment to get your stuff, including your couches, from point A to point B fast, and most importantly, safe.
These companies have proven themselves to be just as effective as most moving trucks, for a reduced cost. And of course, they are environmentally safe, and they are a pretty cool novelty service to use. Imagine telling all of your friends your movers transported your couch on a bike. The looks of confusion will be priceless.