When I open a new tab, I want it to open with my home page, why cant Firefox do this ?

Because Firefox now lacks a setting for being able to do that. (It was getting by malware too often.)

But there is an extension which adds that feature to Firefox. https://addons.mozilla.org/en-US/firefox/addon/new-tab-homepage/

Note that you can middle-click the toolbar Home button to open the home page ids an new tab, so you do not really need an extension.