Is it really necessary to remove our wisdom tooth?

That depends. If they are bothering you and/or have an infection than the only way to solve this problem is to have them removed. As this can be complicated in an adult you must have this done by an oral surgeon, not a general dentist. If they do not bother you and do not show signs a cysts forming upon radiographic exam, than leave then alone. Your dentist and/or oral surgeon should be able to guild you.
Selective procedure. The removal of wisdom tooth is frequently recommended. This requires selective surgical procedures that are individualized according to your individual need.
Depends. If they cause problems - are impacted, are crowding the other teeth, you may want to consider having them removed. If not causing any problems, you probably do not have to worry about them.
Wisdom teeth. The reason wisdom teeth need to be removed is that they often are impacted (crooked) when they come in. When they come in incorrectly other teeth in the mouth will move out of place as well. Bottom line... If they aren't causing issues, though, they don't need to be removed - see a dentist or an oral surgeon for an opinion.
No, but. No. If the wisdom teeth erupt fully in the mouth like the other teeth, can be treated like other teeth. However, in most patients not enough room and problems will eventually occur. Best advice is to see oral surgeon for exam/recommendations.