Delivery cyclists tend to only use the sidewalk for part of the last block when that's the only way to get to their destination. They're definitely not using the sidewalk for the entire trip; that's way too slow. Especially not on e-bikes!
They use it for a block in each direction - coming and going. Now multiply that by the number of delivery drivers and the number of deliveries and its actually quite constant, especially below 14th st. It's most certainly not necessary as they could just easily dismount on the street in front of the building. And yes often it is e-bikes and these are now the preferred delivery bike.
