why would a general-purpose distro not add users to sudoers file?

I tried a different distro, and found that I could not sudo because the distro's default policy apparently was to not add users to the sudoers file. Fine, so I'll re-learn how to edit sudoers--I haven't had to do it manually in many years. I just wonder why a general-purpose distro like the one I'm using would not add me to sudoers automatically. I can understand why some security-niche distro would not; but otherwise...who doesn't need to sudo? How would one keep their software upgraded, and avoid using root, if they can't sudo?