It isn't just 1kg difference overall. This bike weighs less than half of most electric bikes, comparable to an entry level road bike. ~8lbs less than a similarly priced lightweight electric bike with an aluminum frame(Specialized Turbo Vado SL), or a modern non electric commuter bike with fenders and a basket. There are some other carbon fiber ebikes, but they tend to be much more expensive and also are usually heavier(but with a longer battery range)
It isn't just about carrying it up the stairs to your apartment, it is the stairs taking the subway and getting off, getting on and off buses, going up and down stairs for parking garages when you get where you are going, the battery lasting a little longer overall, taking hills and accelerating a little faster. Especially for someone who is not a typical fit cyclist, the weight difference can be a the difference between this and not cycling at all.
For relatively short trips, mixing with public transit an electric kick scooter is a competitive option, cheaper, comparable weight or lighter. Slower and less utility though
It isn't just about carrying it up the stairs to your apartment, it is the stairs taking the subway and getting off, getting on and off buses, going up and down stairs for parking garages when you get where you are going, the battery lasting a little longer overall, taking hills and accelerating a little faster. Especially for someone who is not a typical fit cyclist, the weight difference can be a the difference between this and not cycling at all.
For relatively short trips, mixing with public transit an electric kick scooter is a competitive option, cheaper, comparable weight or lighter. Slower and less utility though