If anything, writing with a hard pen is far more intuitive than sweeping with a brush. It's far easier to find a sharp stick or some other object and draw lines in the sand or carve with it. Who would ever think of using an ox's tail to write? Those things are slow, heavy, and constantly have to be refilled with ink. The worst part is that it's hard to control what you're writing with all those bristles, so why wasn't a sharp pointed object preferred?
First of all, this question - like questions about why Chinese people use chopsticks or have a logographic language - has a high amount of cultural bias. Just because something is easier or makes sense to one personally does not mean mean it is universally the best option for all cultures in all times.
Secondly, ancient Chinese people did use sharp stylus to write. Some of the oldest Chinese writing we have is on bones (known as oracle bones) and inscriptions in bronze, both of which were created with sharpened styluses.
Thirdly, paper was invented in China.
@/u/Talosian_Prav
in addition to the good points raised by /u/blackflag415, it might be worth asking this question to /r/AskAnthropology, as the question itself is probably more suited to their area of expertise than here (so you might get an in-depth response, maybe).