In Git's early history the vast majority of its users were people who significantly preferred the command line interfaces over GUI tools because they can be much quicker (if that is how you work normally at least) and easier to automate. In fact at first there were no GUI tools at all. There is an amount of momentum in tutorials being written for the command line, so people learn from the command line, so people write their procedures/tutorials/other from that perspective.
And it makes sense to learn the basics in its native form and then learn the useful trinkets that are added on top - then your initial learning is restricted to the core so you are learning that which is transferable to all Git front-ends rather than learning specific to a particular GUI.
The way advanced users tend to work in my limited experience (I'm am very much not an advanced user) is to use the command line for the basic day-to-day working and then the GUI tools when anything more complicated (large and/or partial merges) is required.
And it makes sense to learn the basics in its native form and then learn the useful trinkets that are added on top - then your initial learning is restricted to the core so you are learning that which is transferable to all Git front-ends rather than learning specific to a particular GUI.
The way advanced users tend to work in my limited experience (I'm am very much not an advanced user) is to use the command line for the basic day-to-day working and then the GUI tools when anything more complicated (large and/or partial merges) is required.