Of course you could do it the easy way and just buy the players you need, or you could be more developmental in nature.
However, in my opinion, developing consistent winning teams from grass-root level is far more beneficial to the long-term sustainability of the sport.
By building junior teams, within clubs, that will eventually feed into the senior teams, clubs create an upward progression as well as an internal competitiveness. Only when athletes realise that there is always someone else working to take his/her place, can such athlete realise his/her own true potential.
National Teams are thus utterly dependant on the development of club teams.