The Builder Menu shows all available building upgrades. It gives you recommendations for upgrades, that are geared to increase your offensive power.
The Builder Menu allows Chiefs to be smarter with the resources that they have, especially after moving to a new Town Hall level. Following the suggested upgrades are meant to make the transition to a new Town Hall level smoother.
Seasoned Chiefs can of course continue to plan their upgrades any way they wish. For them, it might be useful to have visibility on all of the available upgrades.