Whose "interest of security" are you referring to? If it's the security of Eastern European countries like Georgia and Ukraine, it's self-evident that counties would want to join NATO. If it's existing NATO members, there may be a general interest in expanding to countries who are under threat by the country that caused NATO to be formed in the first place.

Blaming this situation on NATO is like shooting someone with a gun and then blaming them because they bought a bullet proof vest because they were concerned that you would shoot them with a gun.