It is perfectly fine to accept a spot on the waitlist, but you should proceed as if you will not get off the wait-list. Get excited about your top the college that has accepted you, buy the t-shirt, send in the deposit, and fully embrace being a [insert school nickname here]. If you do this and are one of the few people to get in off the wait-list at one of the Ivy League schools, it will be a pleasant surprise. If you hang your hat on getting in off the wait-list and don't get in, you will be devastated. (We see this happen all of the time here at CC).
Also, I agree with @CU123 above. Yield plays a key role here. If Columbia offers 2000 students and expects 1500 to accept, but 1600 accept, they are not taking anyone off the wait-list. (Note: I chose these #s as an example arbitrarily - I have no idea how many offers they extend or how many students/class.) Additionally, I don't know that the "majority" of students who apply to HYP also apply to the other Ivies. Additionally you incorrectly assume that students who apply to HYP as well as the other Ivies will choose HYP other the others. Based on area of study, campus life, location, etc a student who gets accepted at HYP may choose a different Ivy.
Alas, I will never understand this fascination with Ivy League schools. Of course these schools are great, but so are many others.
No, you should not contact colleges about what they consider a hook. They likely won't tell you. Apply for schools that you are realistically qualified to attend (matches), schools where you are in the top 25% (safeties), and a few reaches, if desired. Then let the chips fall where they may.