Simply because Rias grew to become more mature, he passed this role to Issei, although Rias was upset and said she failed to head Issei executing it, but closely rejected Sirzechs with carrying out this sort of things. Inspite of becoming dismayed by her brother's abnormal clearly show of passion https://vivushirt.com/product/qtr-likauce-i-love-highschool-dxd-rias-gremory-t-shirt/