I understand your point, but don't agree completely. I speak American English natively and "waiting on" and "waiting for" are used interchangeably. Also, much like French, context is used to determine whether one is talking about waiting "hand and foot" on someone else when "waiting on" is used.
I am American and speak American English. I agree with you here. "Waiting on" although it can be used to mean "waiting for" it is more a form of slang and not actually correct usage in english, although you will be understood. Ex: "I am waiting on my friend," does not actually mean I am serving him or her, it does mean I am "waiting for them", but it is a slang usage and the inference will be understood from the context in which it is used.
I totally agree with you, karen964959. I am an American teacher, and though both "meanings" will be understood, the proper meaning of "waiting ON" is when someone is serving someone else, like a waiter/waitress. "Waiting FOR" involves the time element it takes for someone or something to come to pass or arrive. Once again, improper English has morphed into slang and is becoming accepted by some. Duo usually teaches proper grammar, not slang.
You were probably thinking of the expression "attendre un bébé" as meaning "to be pregnant". http://www.larousse.com/en/dictionaries/french-english/attendre/6209
Do you mean "waiting for their arrival"? "serving them dinner"? "to wait on" usually indicates serving them. As Kamalynsky and longpshorn have pointed out, there are some common uses in English and "wait for" and "wait on" may be used interchangeably, but there are nevertheless differences in these two expressions.
Have you not read any sentence forum page nor taken a look at the Tips&Notes on every lesson, since you started the course?
Liaisons are explained very early in the course.
This might help you: http://french.about.com/library/pronunciation/bl-liaisons.htm
"I am waiting" is the verb "to wait" in continuous present.
In French, the verb is "attendre" and there are no continuous tenses.
Therefore, "I am waiting" should translate to "j'attends" (simple present) or "je suis en train d'attendre" (the phrase "en train de + infinitive" means "in the process of").
Besides, "to wait" has an indirect object introduced by the preposition "for", but the French verb "attendre" has a direct object; therefore "for" must not be translated.
"Être en attente" is generally "to be on hold" (like on the phone), but you would not use it if you are just waiting for someone or something.
You may see or hear "je suis en attente pour..." but the next word should be a verb in infinitive: "je suis en attente de/pour passer une radio" = "I am on hold for an X-ray".
If you hover on "j'attends", you should see "(I) am waiting for" as the first hint. It is the correct translation.