This should have been agreed on in 1994...They should have know that Russia would never give up their claims on Crimea.
Countries hold onto all sorts of illusions.
After 1871, France devoted its foreign and military policy to securing the return of Alsace-Lorraine; getting what Hitler said was “a worthless sandy strip of soil,” cost the French untold wealth and hundreds of thousands of lives.
Argentina has insisted on the return of the Falkland Islands, despite defeat in war and the repeatedly expressed desire of the residents to remain British.
Even today, we read of rumblings in Mexico contemplating the return of land lost to the US in 1848.
The only two countries I can think of that accepted the loss of territory with a degree of good sense have been Turkey and Germany. But such actions are rare.