Here's why:

* Oxygen is paramagnetic: Oxygen molecules have unpaired electrons, which makes them slightly attracted to magnetic fields. This is called paramagnetism. However, the attraction is very weak.

* Liquids are not easily magnetized: Liquids, in general, are not as easily magnetized as solids. The molecules are more free to move around, making it harder for their magnetic moments to align.

Therefore, while oxygen is slightly paramagnetic, the attraction to a magnet is not strong enough to be noticeable in liquid form.

It's important to note that some other materials, like iron, are ferromagnetic, meaning they are strongly attracted to magnets. This is why a magnet can pick up an iron nail, but not a drop of liquid oxygen.