The World Cup would lose it's special feeling if every two years.
However, if we used performance in the World Cup and Euros to determine the qualification for the next tournament we could get rid of the tedious qualifying during the season. Teams not in the competition could play-off for a chance at the next one in the period when qualified teams play their friendlies and then there could be a few play-offs during the season. The international slots during the season could be reduced to a minimum.
Meanwhile ...