The strongest reasons are **preventing tipping and keeping the countertop’s supports fixed and level**. Your plumbing and caulking concerns are additional benefits.

- **Tipping:** Loaded drawers move weight forward when opened. Someone leaning on an open drawer—or a child climbing it—adds an overturning force. A heavy cabinet may feel stable during ordinary use without being stable under those conditions. IKEA explicitly requires anchoring its base cabinets for safety. [IKEA guidance](https://www.ikea.com/ca/en/customer-service/knowledge/articles/6254dcg1-716f-4e87-99f3-c7f5468dfd73.html)
- **Alignment and support:** Installers shim cabinets level, fasten neighboring cabinets together, and secure them in position. That establishes a stable support for the countertop and keeps doors and drawers aligned. KraftMaid specifies this installation sequence. [KraftMaid installation guide](https://homedepot.kraftmaid.com/wp-content/uploads/2020/08/KraftMaid-Care-Cleaning-Guide.pdf)
- **Connected parts:** A typical continuous countertop ties several cabinets together. Moving one cabinet can strain countertop joints, disturb its support, or pull on sink connections. Larger plumbing holes provide clearance, but don’t make the connections movable.

**The wall is simply a convenient anchoring point.** Islands demonstrate that wall attachment isn’t essential: KraftMaid instead requires those cabinets to be secured to floor blocking. [Installation guide](https://homedepot.kraftmaid.com/wp-content/uploads/2020/08/KraftMaid-Care-Cleaning-Guide.pdf)

Your maintenance advantages are real for independently movable units with their own tops. A kitchen designed around freestanding furniture can provide them. Ordinary fitted cabinetry, however, is designed to work as a fixed assembly; leaving out the wall screws alone doesn’t give it the stability or independence of freestanding furniture.