Sufficiently-developed concentration gives you access to the jhanas, which are extremely blissful states of consciousness. Having reliable access to high valence reduces your need to seek pleasure in less wholesome things (drugs, food, twitter, etc.)

Sufficiently-developed attention gives you insight into how your brain is constructing what you perceive as reality, leading to a reduction in ego, permanent reduction in baseline suffering, and a pervading sense of unity with the rest of the universe.