In walkins companies welcome a bulk of candidates to attend and take interviews. In such cases interviewer don't give proper time to listen and understand answers given by candidate. Also, they don't give options more as they are in hurry to attend all candidates soon. So, they just fire questions one by one frequently and expect answers same way. Unfortunately, a candidate having knowledge and experience may not explain properly and due to this he wouldn't be selected. It is just a luck you get selected or not.
Companies have more options and that is why candidates are not given proper importance as normally thay are given in an appointment. In walkins candidates have to wait for long duration.
Some candidates find it good because of some reasons as i explained earlier about luck like questions asked were already remembered so they will answer without any delay and get selected whether they have logical mind or not.
This is my point view about walkins.