I probably didn't make this clear enough! What I should have said is, "Why is the -ent on the end of the ils and elles forms of French verbs in the present tense not pronounced?" Any ideas on this would be greatly appreciated!
The French do not pronounce this because it would sound like the -ez form or possibly the -ons form of the verb. There are plenty of things that occur in every language that just are...it's just part of the learning process! But this is the best explanation I've gotten so far.