new sites on multisite not https

Dear support team

I want to run a multisite network on My users should be able to setup their own site on that network.

On my server I use ssl wildcards. If I add a new site on the network (for example on the frontend the ssl works fine. I go to the backend and load up an image then the image link shows http://..... If I go - as a superadmin - to the site settings I see the link: I now can manually change it to and the whole backend works well with https. My problem is: I don't wanna do those changes for all my sites manually! Why does "Add new site" not take https as a default setting? Could you please help me with that issue?