Why animals are preserved in science laboratory are kept in glass jars not in steel jars?

Because: We can't see, if animals preserved in steel jar. But in case of glass jars we can easily see animals and birds, whatever living things in lab. Those all are kept in glass jars only.

Because of nicely study about particular animals or plant.

And one important thing is that, in wet specimen glass jar, the liquid in which organism are kept is formaldehyde. So formaldehyde is corrosive to carbon steel.

So therefore, steel is not taken in use for preserved organism in jar.