this is because LiFePO4 batteries are usually made with 26700 3,300mAH cells in 11S3P and 11S4P giving you 10AH to 13.2AH batteries, weighing 4kgs-5kgs.
Li-ion batteries are usually made in 10S with 18650 2,900mAH, 3,300mAH or 3,500mAH cells. A common size of e-biike battery is 13AH or 500WH...