The false front is often a plumbing compromise
Many vanities appear to have a top drawer beneath the basin, but the front may be fixed because the trap and waste occupy the space behind it. That is not automatically poor workmanship; some basin and plumbing combinations genuinely require the compromise.
But it should be a deliberate decision rather than the default result of installing the cabinet after the plumbing.
Design the conflict early
The basin’s waste position, trap shape, drawer height and plumbing route should be drawn together. In some designs, a shaped drawer, revised waste route or approved space-saving connector can preserve more usable storage.
The exact solution depends on the basin and system. A connector suitable for one manufacturer’s furniture should not be assumed to work with a custom cabinet or a different basin.
Useful storage beats decorative symmetry
A vanity is successful when it stores what the household uses and remains easy to clean and service. A perfectly symmetrical elevation with half its drawers unusable may be less successful than a slightly more complex arrangement with accessible storage.
The cabinetmaker and plumber should agree where the service void begins and how the drawer is removed if the trap needs attention.
Read why the basin waste can destroy drawer storage, or see double vanity planning.