There are many valid reasons to have a tree removed:
Dead trees should be removed or they will create a potential hazard. If a tree is large and covers a wide area, extreme caution will be required. Large, dead or dying trees lose stability and can easily fall, especially during severe weather events with high winds or heavy rains. You do not want a large dead tree falling and damaging your property or your neighbor's property.
There are many legitimate reasons to remove living trees as well. The majority of the time a living tree is removed due to renovations on the property. Also, when trees are planted too close to your home or building they may eventually grow too large and start to destroy the property. Therefore, it often comes down to either removing a problem tree now, or paying to fix the damage later!