Last year, I used a service and they required travel info (ticket/hotel/itinerary). Not sure how necessary it was but it could be they just wanted to have all their potential ducks in a row before submitting my application.
I was a bit worried because I was flying into Iguazu and immediately taking a taxi to Argentina so that I would be in Brazil for about 15 mins (this meant no flight to show I was leaving the country). They did question this and I provided a reservation at the Sheraton Iguazu in Argentina and that satisfied everyone.
The other thing - with accomodations, it's pretty easy to make a cancellable hotel reservation if that's ever necessary to get the visa processed.
I ended up with a 10-year, multi-entry visa so it worked out OK.