Because gel pens save water and are much more convenient than pens. Moreover, the tip of gel pen does not scratch paper, and the water is smooth (there may be some brands with unstable quality and poor water outlet). But its advantages should make up for its disadvantages greatly.
So now many hard-pen calligraphy lovers are practicing writing with gel pens.
If you practice writing with a gel pen, it is recommended to use a slightly thicker specification. For example, 0.7,1.0mm.
The words written in this way can easily reflect the change of force. If written well, it will have the charm of a brush.