The brushless geared hub motor which is used in the MAD | CAT fat tire ebike has become more widespread in recent years.
There are a number of advantages.
To begin with, the motor does not create friction, allowing freewheeling. While it does not have regenerative power; it allows you to pedal the bicycle like any regular bike.
One of the biggest pluses of hub motors is that they require little or no maintenance. There are simply less parts to fail. This is an independent system that retains all of the components inside the motor casing.
In the geared hub, over time, a tooth can break off and the reinforced nylon gear, but it is a replaceable part and a straight forward fix.
Hub motors don’t connect to the main pedal drive system; you can lose your chain and still get home on the motor, and vice versa. These motors also don’t add any extra stress to the chain or shifters, and don’t cause any of those parts to wear out quicker.
The hub motors also do not cost nearly as much as mid drive motors.