Why does glTranslatef() resize object?

I have 3 rectangles and I need to place them in shape of podium. At this moment they look like this:

Code of display func:

    glPushMatrix();
    glRotated(rotate_x, 1.0, 0.0, 0.0);
    glRotated(rotate_y, 0.0, 1.0, 0.0);
    glScalef(1, 3, 1);
    glColor3fv(gold);
    glutSolidCube(2);
    glPopMatrix();
    
    
    

    
    glPushMatrix();

    glTranslated(2, 0, -3);
    glRotated(rotate_x, 1.0, 0.0, 0.0);
    glRotated(rotate_y, 0.0, 1.0, 0.0);
    glScalef(1, 2, 1);
    glColor3fv(silver);
    glutSolidCube(2);
    glPopMatrix();


    glPushMatrix();
    glTranslatef(-2, 0, 0);
    glScalef(1, 1, 1);
    glRotated(rotate_x, 1.0, 0.0, 0.0);
    glRotated(rotate_y, 0.0, 1.0, 0.0);
    glColor3fv(bronze);
    glutSolidCube(2);
    glPopMatrix();

When I try to move silver rectangle a liitle bit down to make it on same level as yellow one by using glTranslatef(-2, 0, -2); it just becomes smaller:

The first two parameters of glTranslatef works just fine moving object left/right and closer/further, so why does third parameter changes object's size?

You moved it farther away. Objects which are farther away appear smaller; that's just how perspective works. And since you have no lighting, background objects, or any other depth cues, being farther away is visibly identical to scaling it to a smaller size.