This is just Kozmo.com 2.0
It is easier to imagine if you consider that it is likely safer for a dealer to simply travel to their customers. One attracts too much attention if they have random people showing up at their residence, or takes on more risk if they have to meet under the public eye. Customers share in this decreased risk.
It also provides low level dealers a competitive advantage in markets they don't have locked down. It might be more of a necessity than optional service these days.
With cats, I suppose couriers might refuse them -- walking down the street with a cat carrier would be kind of unpleasant, and it would be worse on a bike.
But I honestly doubt anyone ever trusted us with drugs, the most memorable things I delivered were A) a pee cup (luckily empty) and B) an industrial size sink from Wall St. to 42nd.
I can already imagine lawyers having a field-day on the words ‘possible illegality’.