not only woudl it spill, or airborne pathogens contaminate. another was evaporation of water and other chemicals that keep the solution at the right viscosity and PH. if the salts that are added to mimic are concentrated you change the ph and can damage the eye or ruin the lens by not allowing the proper rehydration...
have you ever seen teh edge of a solution bottle with that papery plastic film residue..... thats result of being exposed to air....

j