when trying to install Ruby, Vagrant, and Grunt using terminal I am still required to use sudo on my installs. I am sole proprietor of the laptop and have an administrator account. Shouldn't I be able to install software without using sudo?
Even though the account is an administrator, you still need to use sudo to become the root user. Administrator still has restrictions on what files can be read or written to.
For example, the /System/Library/User Template/ folder is set to System: Read/Write and even though you are an administrator, you won't be able to open this folder without either changing the permissions or using sudo to become the root user.
This is by design. The vast majority of users want to install GUI software and adjust system settings, but do not want to install command-line software. Those same users would prefer malware have a harder time getting into the process, and often need to be protected from themselves ("Library"? Don't need a folder of books...). So the admin user is not root.
Those users who are familiar with the Unix layer know about sudo, and should also know how to add specific commands to sudoers when needed. There's also the
sudo bash method of getting a root shell.
No, you need to use sudo because you are not root user (good thing, because you don't want to accidentally wreck the computer), sudo allows you to momentarily "become" root. If you were not an administrator, you are not one of the privileged users that are allowed to use
sudo, and thus, you would not be able to install anything requiring