Slightly tangential, but in fact all flight reservations through a travel agency are initially made without payment. The entire process is quite complex, due to compatibility with processes and systems that were built in the 70s... The flow is to create the booking (and hence receive a record locator or PNR), and then to attach a form of payment. If the payment matches the cost, it is then possible to request ticketing, at which point a ticket number will be generated, which is the "real" confirmation
I am a Turkish citizen, and we need a visa to visit EU member countries. You are not 100% sure if you will get the visa, so may want to make a flight and hotel reservation first, and then buy them if you get the visa. So reserving the tickets is preferred.
Maybe, but other countries still have it. Vietnamese have one of the worst passports on the planet. Their govt. won't let them leave without proof that they will come back, usually in the form of a job, cash in the bank, spouse and tour or reservation based trips.
Many airlines require you to have an onward flight out of a country before they will let you fly into it. This allows you to fulfill the technical requirement without having to pay for a plane ticket you aren't planning to use.
A reservation that is not paid is not ticketed. A reservation that is not ticketed is not 100% guaranteed
But I agree that this is till a problem for airline inventory management, and an online travel agency should definitely not be opening this feature to the general public!
There are several usecases that require unpaid reservations, the most common one nowadays is corporate travel, when you need to integrate approval flows - the approval step will be between the reservation and the ticketing.
Like just about every industry, there is a world of complexity hidden underneath the surface :)
https://matrix.itasoftware.com/ to get detailed fare rules & restrictions
https://www.expertflyer.com & https://itunes.apple.com/us/app/seat-alerts/id533533342
https://www.checkmytrip.com/ allows entering name & booking-reference and gives all detail
https://www.viewtrip.com/
https://tripcase.com will use name + booking-reference to get detailed PNR information including the first name
https://www.fly.kiev.ua can make a flight reservation without a payment, still gives an 6char booking-reference