Why is it not advisable to wear contact lenses in lab?
Because dangerous substances (e.g. acids, bases, and other painful fluids) can penetrate them, and get stuck underneath them. Furthermore, if you find yourself unconscious and the medics (or whoever someone else called) come in, the last thing they will look for is contact lenses in your eyes. They always search the lab for spills and other hazards, and not necessarily inspect your eyes as thoroughly.
So, it is a must to wear proper safety goggles with at least side-shields. Z87's are a common, sufficient brand that I use at my university when I TA.