Why did the school teacher steal to recommend the direct liquid ballpoint pen?

Why did the school teacher steal to recommend the straight liquid ball pen? The disadvantage of straight liquid ball pen is that there is no way to replace the refill. Direct liquid ballpoint pen is neither a ballpoint pen nor a gel pen. It is the best writing performance and quality among pen products at present. A straight liquid ballpoint pen consists of a pen cap, a pen head body, an ink reservoir and a pen holder. After talking about the ink supply structure of the pen, we began to say "straight liquid ballpoint pen", which can be understood as a combination of pen and ballpoint pen (such as a pen with a spherical nib).