Probably it's because western countries are no longer on the front lines and so rapid expeditionary deployment is preferred over the tactical versatility but logistically more maintenance-intensive tracks. You also have the factor that modern SPGs and ammo can fire further, so you have a wider selection of accessible firing positions, negating the need for tracks. In Israel's case, while the country is small there are threats on all sides, so rapid/simplified deployment to swing between theatres is a crucial advantage.