Because there has been a mini-bubble in the "on-demand economy," a.k.a., delivery businesses. Investors are highly subject to groupthink and trend chasing. When one or more companies start to take off in the same space, a category is (theoretically) born. And then everyone wants exposure to the category.
Now, in the public markets, there's no problem jumping into a category; just buy some stock in X, Y, Z companies. But in the private market, if you didn't get in on X company's Series Y, you can't just buy in tomorrow to gain some exposure. So you invest in the next company with a similar concept (but perhaps in a different vertical).
All the while, nobody stops to think whether the newborn category they're chasing is even fundamentally viable, or if viable, whether it's nicely profitable at scale. Or whether it can bear so many entrants into the space.
Now, in the public markets, there's no problem jumping into a category; just buy some stock in X, Y, Z companies. But in the private market, if you didn't get in on X company's Series Y, you can't just buy in tomorrow to gain some exposure. So you invest in the next company with a similar concept (but perhaps in a different vertical).
All the while, nobody stops to think whether the newborn category they're chasing is even fundamentally viable, or if viable, whether it's nicely profitable at scale. Or whether it can bear so many entrants into the space.