Boats are like a Swiss Army knife in rescues:

• Transportation - A boat is typically the fastest way to reach a victim.
• Ambulance - A raft or canoe can safely carry an injured boater downstream.
• Barge - A boat can carry a fair amount of rescue gear, even kayaks.  Check out Ron Ray's kayak some time - LOL.  Besides the mandatory throw rope, some carry folding saws, pin kits, first aid kits, food & water, extra clothing, spare paddles, etc.  Try not to go overboard.
• Tow Truck - Along with a rescue vest and tether, you can tow pretty much any boat, swimmer, or paddle - sometimes all three at once.
• Messenger - The boat is the fastest way down stream to request assistance.  On easier water, a kayak can go back upstream pretty quick as well.
• Crane or pier - You can assist someone in trying to right their boat via a hands of god maneuver or a bow rescue.
• Drainage - You can quickly empty water by dragging their boat upside down over yours.
• Bulldozer - You can plow a swamped boat to shore.
• Sea Anchor - You can pull a boater trapped in a hydraulic out from a safe distance using fast current to assist.
• Life Raft - In big water, most PFDs have a tough time staying on the surface.  A boat with air bags is like a mega-PFD.
• There are other uses as well like a quick shelter on land.  Use your imagination.