As you know that, In chemistry and physics , we have a lot of logical, experimental and most importantly, calculative work.So we need such a script which takes less time to write and could be understood by all. Thats why we use chemical formulae to express chemicals in chemistry...and we use symbols in physics (such as electric circuit symbols) to make our writing work less and fast, giving us more time for more important works.
Hope this basic explanation will help :-)
P.S. i myself don't like complex explanations :-)