Crime Free - tourists don't want to visit an area with high crime rates because they want to be safe. They want to be able to relax and feel safe without being on guard, constantly watching their belongings.
Political Stability - If there's a chance of war or anything like that then tourists will feel unsafe if things may happen to them and jeopardize their safety.
Healthy Environment - Toursits want a clean area, no litter, no diseases etc.
No one wants to go on holiday to a country where they are likely to get stabbed/robbed/catch a disease/get caught up in a war. Tourists want to relax. For countries trying to develop their tourism industry they have to make sure they are giving tourists what they want - a relaxing, enjoyable and safe holiday. If they cannot provide a safe area then no one will want to visit.
